CVE-2026-117666

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-117666", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-10-30T10:00:01.681Z", "datePublished": "2026-10-30T20:22:16.466Z", "dateUpdated": "2026-11-06T16:02:49.781Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["ssl_verify_hostname"], "packageName": "ssl_verify_fun", "packageURL": "pkg:hex/ssl_verify_fun", "product": "ssl_verify_fun", "programFiles": ["src/ssl_verify_hostname.erl"], "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "versions": [{"lessThan": "1.1.8", "status": "affected", "version": "1.0.1", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["ssl_verify_hostname"], "packageName": "deadtrickster/ssl_verify_fun.erl", "packageURL": "pkg:github/deadtrickster/ssl_verify_fun.erl", "product": "ssl_verify_fun", "programFiles": ["src/ssl_verify_hostname.erl"], "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "versions": [{"lessThan": "ca34031299cd2e0c98794c0da4ba556b94e39aad", "status": "affected", "version": "a49ca56923356c7a3981692b23c42ef32c2990e0", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in <code>ssl</code> before the user <code>verify_fun</code> is called with <code>valid_peer</code>, as long as <code>server_name_indication</code> is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets <code>{server_name_indication, disable}</code>, when a TLS server uses <code>ssl_verify_hostname:verify_fun/3</code> to verify client certificates, when it calls <code>ssl_verify_hostname:verify_cert_hostname/2</code> directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI.</p>"}, {"base64": false, "type": "text/markdown", "value": "ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in `ssl` before the user `verify_fun` is called with `valid_peer`, as long as `server_name_indication` is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets `{server_name_indication, disable}`, when a TLS server uses `ssl_verify_hostname:verify_fun/3` to verify client certificates, when it calls `ssl_verify_hostname:verify_cert_hostname/2` directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI."}], "value": "ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in ssl before the user verify_fun is called with valid_peer, as long as server_name_indication is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets {server_name_indication, disable}, when a TLS server uses ssl_verify_hostname:verify_fun/3 to verify client certificates, when it calls ssl_verify_hostname:verify_cert_hostname/2 directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.1.8", "versionStartIncluding": "1.0.1", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Andrew Moore"}, {"lang": "en", "type": "finder", "value": "Martin Karrer"}, {"lang": "en", "type": "reporter", "value": "Andrew Moore"}, {"lang": "en", "type": "remediation developer", "value": "Martin Karrer"}, {"lang": "en", "type": "remediation developer", "value": "deadtrickster"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "dateAssigned": "2026-10-30T10:26:35.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. <code>try_match_wildcard/4</code> in <code>src/ssl_verify_hostname.erl</code> anchors only the text before and after the <code>*</code> of an identifier such as <code>f*.example.net</code>, so the wildcard also consumes dots and the certificate is accepted for <code>f.evil.example.net</code>. RFC 6125 confines a wildcard to the left-most label. The same matcher lets <code>*.168.1.1</code> match the IP literal <code>192.168.1.1</code>. Whole-label wildcards are matched correctly.</p>\n<p>Erlang/OTP 20.0 and later check the hostname in <code>ssl</code> before a user <code>verify_fun</code> sees <code>valid_peer</code>, so a client that keeps <code>server_name_indication</code> set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of <code>verify_cert_hostname/2</code>.</p>\n<p>This issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.</p>"}, {"base64": false, "type": "text/markdown", "value": "Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. `try_match_wildcard/4` in `src/ssl_verify_hostname.erl` anchors only the text before and after the `*` of an identifier such as `f*.example.net`, so the wildcard also consumes dots and the certificate is accepted for `f.evil.example.net`. RFC 6125 confines a wildcard to the left-most label. The same matcher lets `*.168.1.1` match the IP literal `192.168.1.1`. Whole-label wildcards are matched correctly.\n\nErlang/OTP 20.0 and later check the hostname in `ssl` before a user `verify_fun` sees `valid_peer`, so a client that keeps `server_name_indication` set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of `verify_cert_hostname/2`.\n\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8."}], "value": "Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. try_match_wildcard/4 in src/ssl_verify_hostname.erl anchors only the text before and after the * of an identifier such as f*.example.net, so the wildcard also consumes dots and the certificate is accepted for f.evil.example.net. RFC 6125 confines a wildcard to the left-most label. The same matcher lets *.168.1.1 match the IP literal 192.168.1.1. Whole-label wildcards are matched correctly.\n\nErlang/OTP 20.0 and later check the hostname in ssl before a user verify_fun sees valid_peer, so a client that keeps server_name_indication set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of verify_cert_hostname/2.\n\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8."}], "impacts": [{"capecId": "CAPEC-94", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>A holder of a certificate for <code>f*.example.net</code> from a CA the client trusts can impersonate any host named <code>f.&lt;label&gt;.example.net</code> to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection.</p>"}, {"base64": false, "type": "text/markdown", "value": "A holder of a certificate for `f*.example.net` from a CA the client trusts can impersonate any host named `f.<label>.example.net` to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection."}], "value": "A holder of a certificate for f*.example.net from a CA the client trusts can impersonate any host named f.<label>.example.net to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection."}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 9.1, "baseSeverity": "CRITICAL", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-297", "description": "CWE-297 Improper Validation of Certificate with Host Mismatch", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-10-30T20:22:16.466Z"}, "references": [{"name": "ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary", "tags": ["vendor-advisory", "related"], "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw2-hphm-c5px"}, {"name": "EEF CNA record for CVE-2026-117666", "tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-117666.html"}, {"name": "OSV record EEF-CVE-2026-117666", "tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-117666"}, {"name": "Do not let partial-label wildcards match across label boundaries (ssl_verify_fun.erl pull request #33)", "tags": ["patch"], "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/pull/33"}, {"name": "Introducing commit a49ca56 in deadtrickster/ssl_verify_fun.erl", "tags": ["related"], "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a3981692b23c42ef32c2990e0"}, {"name": "Fix commit ca34031 in deadtrickster/ssl_verify_fun.erl", "tags": ["patch"], "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794c0da4ba556b94e39aad"}], "source": {"discovery": "EXTERNAL"}, "title": "ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>On Erlang/OTP 21 or later, keep <code>server_name_indication</code> set to the target hostname and pass <code>{customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]}</code> in the <code>ssl</code> options. The hostname check in <code>ssl</code> then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options.</p>"}, {"base64": false, "type": "text/markdown", "value": "On Erlang/OTP 21 or later, keep `server_name_indication` set to the target hostname and pass `{customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]}` in the `ssl` options. The hostname check in `ssl` then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options."}], "value": "On Erlang/OTP 21 or later, keep server_name_indication set to the target hostname and pass {customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]} in the ssl options. The hostname check in ssl then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options."}], "x_proofOfConcept": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<ol>\n<li>Issue a leaf certificate whose only <code>subjectAltName</code> entry is <code>dNSName</code> <code>f*.example.net</code>, for example with <code>public_key:pkix_test_data/1</code>, and decode it with <code>public_key:pkix_decode_cert(Der, otp)</code>.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\")</code>. It returns <code>{valid, \"foo.example.net\"}</code>, as expected.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\")</code>. It returns <code>{valid, \"f.evil.example.net\"}</code> although the hostname spans two labels where the wildcard sits.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\")</code> as a control. It returns <code>{fail, unable_to_match_altnames}</code>.</li>\n<li>For the IP-literal variant, issue a leaf with <code>dNSName</code> <code>*.168.1.1</code> and call <code>verify_cert_hostname(Cert, \"192.168.1.1\")</code>. It returns <code>{valid, \"192.168.1.1\"}</code>.</li>\n<li>To observe the full TLS path, serve the first certificate from <code>ssl:listen/2</code> and connect with <code>{verify, verify_peer}</code>, the CA in <code>cacerts</code>, <code>{verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}}</code> and <code>{server_name_indication, disable}</code>. The handshake succeeds. With <code>{server_name_indication, \"f.evil.example.net\"}</code> instead, OTP 20.0 or later rejects the certificate with <code>hostname_check_failed</code> before ssl_verify_fun runs.</li>\n</ol>"}, {"base64": false, "type": "text/markdown", "value": "1. Issue a leaf certificate whose only `subjectAltName` entry is `dNSName` `f*.example.net`, for example with `public_key:pkix_test_data/1`, and decode it with `public_key:pkix_decode_cert(Der, otp)`.\n2. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\")`. It returns `{valid, \"foo.example.net\"}`, as expected.\n3. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\")`. It returns `{valid, \"f.evil.example.net\"}` although the hostname spans two labels where the wildcard sits.\n4. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\")` as a control. It returns `{fail, unable_to_match_altnames}`.\n5. For the IP-literal variant, issue a leaf with `dNSName` `*.168.1.1` and call `verify_cert_hostname(Cert, \"192.168.1.1\")`. It returns `{valid, \"192.168.1.1\"}`.\n6. To observe the full TLS path, serve the first certificate from `ssl:listen/2` and connect with `{verify, verify_peer}`, the CA in `cacerts`, `{verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}}` and `{server_name_indication, disable}`. The handshake succeeds. With `{server_name_indication, \"f.evil.example.net\"}` instead, OTP 20.0 or later rejects the certificate with `hostname_check_failed` before ssl_verify_fun runs."}], "value": "* Issue a leaf certificate whose only subjectAltName entry is dNSName f*.example.net, for example with public_key:pkix_test_data/1, and decode it with public_key:pkix_decode_cert(Der, otp).\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\"). It returns {valid, \"foo.example.net\"}, as expected.\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\"). It returns {valid, \"f.evil.example.net\"} although the hostname spans two labels where the wildcard sits.\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\") as a control. It returns {fail, unable_to_match_altnames}.\n* For the IP-literal variant, issue a leaf with dNSName *.168.1.1 and call verify_cert_hostname(Cert, \"192.168.1.1\"). It returns {valid, \"192.168.1.1\"}.\n* To observe the full TLS path, serve the first certificate from ssl:listen/2 and connect with {verify, verify_peer}, the CA in cacerts, {verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}} and {server_name_indication, disable}. The handshake succeeds. With {server_name_indication, \"f.evil.example.net\"} instead, OTP 20.0 or later rejects the certificate with hostname_check_failed before ssl_verify_fun runs."}], "x_technicalAnalysis": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p><strong>1. Identifier parsing.</strong> <code>ssl_verify_hostname:try_match_hostname/2</code> strips trailing dots, tries an exact case-insensitive match, and otherwise calls <code>parse_and_validate_wildcard_identifier/2</code>. That function accepts an identifier with one <code>*</code> in the left-most label and at least two labels after it, and classifies it as <code>SingleCharW</code> when the label is exactly <code>*</code>.</p>\n<p><strong>2. Whole-label wildcard, correct.</strong> For <code>*.example.net</code> the matcher compares the text after the <code>*</code> with the hostname from its first dot onward, so <code>a.b.example.net</code> fails because <code>.b.example.net</code> differs from <code>.example.net</code>.</p>\n<p><strong>3. Partial-label wildcard, incorrect.</strong> For <code>f*.example.net</code> the <code>SingleCharW</code> branch is skipped. <code>try_match_wildcard/4</code> then checks only that the hostname ends with <code>.example.net</code> and starts with <code>f</code>. Nothing checks the span consumed by the <code>*</code>, so <code>f.evil.example.net</code> and <code>f.a.b.example.net</code> pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The <code>wildcard_not_in_a_label/2</code> guard only rejects internationalized <code>xn--</code> labels and does not help.</p>\n<p><strong>4. IP literals.</strong> The reference identifier is treated as a DNS name whatever its shape, so <code>verify_cert_hostname/2</code> with hostname <code>192.168.1.1</code> matches a <code>dNSName</code> of <code>*.168.1.1</code> through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's <code>ssl</code> converts an IP-literal string to an <code>{ip, ...}</code> reference that only matches <code>iPAddress</code> entries.</p>\n<p><strong>5. Interaction with Erlang/OTP.</strong> When <code>ssl_verify_hostname:verify_fun/3</code> is used as <code>verify_fun</code>, OTP 20.0 and later call <code>ssl_certificate:validate/4</code> for <code>valid_peer</code> before the user fun. In the client role with <code>server_name_indication</code> set to a hostname, or with a peer IP from a socket upgrade, OTP runs <code>public_key:pkix_verify_hostname/3</code> and hands the user fun <code>{bad_cert, hostname_check_failed}</code> instead of <code>valid_peer</code>, which ssl_verify_fun turns into <code>{fail, ...}</code>. OTP's default match function allows no wildcards, and its <code>https</code> match function (<code>public_key:pkix_verify_hostname_match_fun/1</code>) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with <code>{server_name_indication, disable}</code>, in the server role, on direct calls to <code>verify_cert_hostname/2</code>, or on OTP older than 20.0.</p>"}, {"base64": false, "type": "text/markdown", "value": "**1. Identifier parsing.** `ssl_verify_hostname:try_match_hostname/2` strips trailing dots, tries an exact case-insensitive match, and otherwise calls `parse_and_validate_wildcard_identifier/2`. That function accepts an identifier with one `*` in the left-most label and at least two labels after it, and classifies it as `SingleCharW` when the label is exactly `*`.\n\n**2. Whole-label wildcard, correct.** For `*.example.net` the matcher compares the text after the `*` with the hostname from its first dot onward, so `a.b.example.net` fails because `.b.example.net` differs from `.example.net`.\n\n**3. Partial-label wildcard, incorrect.** For `f*.example.net` the `SingleCharW` branch is skipped. `try_match_wildcard/4` then checks only that the hostname ends with `.example.net` and starts with `f`. Nothing checks the span consumed by the `*`, so `f.evil.example.net` and `f.a.b.example.net` pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The `wildcard_not_in_a_label/2` guard only rejects internationalized `xn--` labels and does not help.\n\n**4. IP literals.** The reference identifier is treated as a DNS name whatever its shape, so `verify_cert_hostname/2` with hostname `192.168.1.1` matches a `dNSName` of `*.168.1.1` through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's `ssl` converts an IP-literal string to an `{ip, ...}` reference that only matches `iPAddress` entries.\n\n**5. Interaction with Erlang/OTP.** When `ssl_verify_hostname:verify_fun/3` is used as `verify_fun`, OTP 20.0 and later call `ssl_certificate:validate/4` for `valid_peer` before the user fun. In the client role with `server_name_indication` set to a hostname, or with a peer IP from a socket upgrade, OTP runs `public_key:pkix_verify_hostname/3` and hands the user fun `{bad_cert, hostname_check_failed}` instead of `valid_peer`, which ssl_verify_fun turns into `{fail, ...}`. OTP's default match function allows no wildcards, and its `https` match function (`public_key:pkix_verify_hostname_match_fun/1`) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with `{server_name_indication, disable}`, in the server role, on direct calls to `verify_cert_hostname/2`, or on OTP older than 20.0."}], "value": "1. Identifier parsing. ssl_verify_hostname:try_match_hostname/2 strips trailing dots, tries an exact case-insensitive match, and otherwise calls parse_and_validate_wildcard_identifier/2. That function accepts an identifier with one * in the left-most label and at least two labels after it, and classifies it as SingleCharW when the label is exactly *.\n\n2. Whole-label wildcard, correct. For *.example.net the matcher compares the text after the * with the hostname from its first dot onward, so a.b.example.net fails because .b.example.net differs from .example.net.\n\n3. Partial-label wildcard, incorrect. For f*.example.net the SingleCharW branch is skipped. try_match_wildcard/4 then checks only that the hostname ends with .example.net and starts with f. Nothing checks the span consumed by the *, so f.evil.example.net and f.a.b.example.net pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The wildcard_not_in_a_label/2 guard only rejects internationalized xn-- labels and does not help.\n\n4. IP literals. The reference identifier is treated as a DNS name whatever its shape, so verify_cert_hostname/2 with hostname 192.168.1.1 matches a dNSName of *.168.1.1 through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's ssl converts an IP-literal string to an {ip, ...} reference that only matches iPAddress entries.\n\n5. Interaction with Erlang/OTP. When ssl_verify_hostname:verify_fun/3 is used as verify_fun, OTP 20.0 and later call ssl_certificate:validate/4 for valid_peer before the user fun. In the client role with server_name_indication set to a hostname, or with a peer IP from a socket upgrade, OTP runs public_key:pkix_verify_hostname/3 and hands the user fun {bad_cert, hostname_check_failed} instead of valid_peer, which ssl_verify_fun turns into {fail, ...}. OTP's default match function allows no wildcards, and its https match function (public_key:pkix_verify_hostname_match_fun/1) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with {server_name_indication, disable}, in the server role, on direct calls to verify_cert_hostname/2, or on OTP older than 20.0."}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-11-06T16:02:35.597989Z", "id": "CVE-2026-117666", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-11-06T16:02:49.781Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-117666", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-11-06T16:02:35.597989Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-11-06T16:02:42.864Z"}}], "cna": {"title": "ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Andrew Moore"}, {"lang": "en", "type": "finder", "value": "Martin Karrer"}, {"lang": "en", "type": "reporter", "value": "Andrew Moore"}, {"lang": "en", "type": "remediation developer", "value": "Martin Karrer"}, {"lang": "en", "type": "remediation developer", "value": "deadtrickster"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "impacts": [{"capecId": "CAPEC-94", "descriptions": [{"lang": "en", "value": "A holder of a certificate for f*.example.net from a CA the client trusts can impersonate any host named f.<label>.example.net to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection.", "supportingMedia": [{"type": "text/html", "value": "<p>A holder of a certificate for <code>f*.example.net</code> from a CA the client trusts can impersonate any host named <code>f.&lt;label&gt;.example.net</code> to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection.</p>", "base64": false}, {"type": "text/markdown", "value": "A holder of a certificate for `f*.example.net` from a CA the client trusts can impersonate any host named `f.<label>.example.net` to a client that relies on ssl_verify_fun alone for hostname verification, and read or alter the traffic of that connection.", "base64": false}]}]}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 9.1, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "modules": ["ssl_verify_hostname"], "product": "ssl_verify_fun", "versions": [{"status": "affected", "version": "1.0.1", "lessThan": "1.1.8", "versionType": "semver"}], "packageURL": "pkg:hex/ssl_verify_fun", "packageName": "ssl_verify_fun", "programFiles": ["src/ssl_verify_hostname.erl"], "collectionURL": "https://repo.hex.pm", "defaultStatus": "unaffected", "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}]}, {"cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "modules": ["ssl_verify_hostname"], "product": "ssl_verify_fun", "versions": [{"status": "affected", "version": "a49ca56923356c7a3981692b23c42ef32c2990e0", "lessThan": "ca34031299cd2e0c98794c0da4ba556b94e39aad", "versionType": "git"}], "packageURL": "pkg:github/deadtrickster/ssl_verify_fun.erl", "packageName": "deadtrickster/ssl_verify_fun.erl", "programFiles": ["src/ssl_verify_hostname.erl"], "collectionURL": "https://github.com", "defaultStatus": "unaffected", "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}]}], "references": [{"url": "https://github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw2-hphm-c5px", "name": "ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary", "tags": ["vendor-advisory", "related"]}, {"url": "https://cna.erlef.org/cves/CVE-2026-117666.html", "name": "EEF CNA record for CVE-2026-117666", "tags": ["related"]}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-117666", "name": "OSV record EEF-CVE-2026-117666", "tags": ["related"]}, {"url": "https://github.com/deadtrickster/ssl_verify_fun.erl/pull/33", "name": "Do not let partial-label wildcards match across label boundaries (ssl_verify_fun.erl pull request #33)", "tags": ["patch"]}, {"url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a3981692b23c42ef32c2990e0", "name": "Introducing commit a49ca56 in deadtrickster/ssl_verify_fun.erl", "tags": ["related"]}, {"url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794c0da4ba556b94e39aad", "name": "Fix commit ca34031 in deadtrickster/ssl_verify_fun.erl", "tags": ["patch"]}], "workarounds": [{"lang": "en", "value": "On Erlang/OTP 21 or later, keep server_name_indication set to the target hostname and pass {customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]} in the ssl options. The hostname check in ssl then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options.", "supportingMedia": [{"type": "text/html", "value": "<p>On Erlang/OTP 21 or later, keep <code>server_name_indication</code> set to the target hostname and pass <code>{customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]}</code> in the <code>ssl</code> options. The hostname check in <code>ssl</code> then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options.</p>", "base64": false}, {"type": "text/markdown", "value": "On Erlang/OTP 21 or later, keep `server_name_indication` set to the target hostname and pass `{customize_hostname_check, [{match_fun, public_key:pkix_verify_hostname_match_fun(https)}]}` in the `ssl` options. The hostname check in `ssl` then rejects the mismatch before ssl_verify_fun runs, and legitimate wildcard certificates continue to match. hackney and tls_certificate_check already set both options.", "base64": false}]}], "dateAssigned": "2026-10-30T10:26:35.000Z", "descriptions": [{"lang": "en", "value": "Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. try_match_wildcard/4 in src/ssl_verify_hostname.erl anchors only the text before and after the * of an identifier such as f*.example.net, so the wildcard also consumes dots and the certificate is accepted for f.evil.example.net. RFC 6125 confines a wildcard to the left-most label. The same matcher lets *.168.1.1 match the IP literal 192.168.1.1. Whole-label wildcards are matched correctly.\n\nErlang/OTP 20.0 and later check the hostname in ssl before a user verify_fun sees valid_peer, so a client that keeps server_name_indication set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of verify_cert_hostname/2.\n\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.", "supportingMedia": [{"type": "text/html", "value": "<p>Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. <code>try_match_wildcard/4</code> in <code>src/ssl_verify_hostname.erl</code> anchors only the text before and after the <code>*</code> of an identifier such as <code>f*.example.net</code>, so the wildcard also consumes dots and the certificate is accepted for <code>f.evil.example.net</code>. RFC 6125 confines a wildcard to the left-most label. The same matcher lets <code>*.168.1.1</code> match the IP literal <code>192.168.1.1</code>. Whole-label wildcards are matched correctly.</p>\n<p>Erlang/OTP 20.0 and later check the hostname in <code>ssl</code> before a user <code>verify_fun</code> sees <code>valid_peer</code>, so a client that keeps <code>server_name_indication</code> set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of <code>verify_cert_hostname/2</code>.</p>\n<p>This issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.</p>", "base64": false}, {"type": "text/markdown", "value": "Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. `try_match_wildcard/4` in `src/ssl_verify_hostname.erl` anchors only the text before and after the `*` of an identifier such as `f*.example.net`, so the wildcard also consumes dots and the certificate is accepted for `f.evil.example.net`. RFC 6125 confines a wildcard to the left-most label. The same matcher lets `*.168.1.1` match the IP literal `192.168.1.1`. Whole-label wildcards are matched correctly.\n\nErlang/OTP 20.0 and later check the hostname in `ssl` before a user `verify_fun` sees `valid_peer`, so a client that keeps `server_name_indication` set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of `verify_cert_hostname/2`.\n\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-297", "description": "CWE-297 Improper Validation of Certificate with Host Mismatch"}]}], "configurations": [{"lang": "en", "value": "ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in ssl before the user verify_fun is called with valid_peer, as long as server_name_indication is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets {server_name_indication, disable}, when a TLS server uses ssl_verify_hostname:verify_fun/3 to verify client certificates, when it calls ssl_verify_hostname:verify_cert_hostname/2 directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI.", "supportingMedia": [{"type": "text/html", "value": "<p>ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in <code>ssl</code> before the user <code>verify_fun</code> is called with <code>valid_peer</code>, as long as <code>server_name_indication</code> is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets <code>{server_name_indication, disable}</code>, when a TLS server uses <code>ssl_verify_hostname:verify_fun/3</code> to verify client certificates, when it calls <code>ssl_verify_hostname:verify_cert_hostname/2</code> directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI.</p>", "base64": false}, {"type": "text/markdown", "value": "ssl_verify_fun decides the outcome only where it is the sole hostname check. Erlang/OTP 20.0 and later verify the hostname in `ssl` before the user `verify_fun` is called with `valid_peer`, as long as `server_name_indication` is a hostname or the connection was upgraded from a socket. A deployment is exposed when it sets `{server_name_indication, disable}`, when a TLS server uses `ssl_verify_hostname:verify_fun/3` to verify client certificates, when it calls `ssl_verify_hostname:verify_cert_hostname/2` directly, or when it runs Erlang/OTP older than 20.0. The attacker also needs a certificate with a partial-label wildcard from a CA the client trusts, which the CA/Browser Forum Baseline Requirements do not allow, so the realistic exposure is private PKI.", "base64": false}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.1.8", "versionStartIncluding": "1.0.1"}], "operator": "OR"}], "operator": "AND"}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-10-30T20:22:16.466Z"}, "x_proofOfConcept": [{"lang": "en", "value": "* Issue a leaf certificate whose only subjectAltName entry is dNSName f*.example.net, for example with public_key:pkix_test_data/1, and decode it with public_key:pkix_decode_cert(Der, otp).\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\"). It returns {valid, \"foo.example.net\"}, as expected.\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\"). It returns {valid, \"f.evil.example.net\"} although the hostname spans two labels where the wildcard sits.\n* Call ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\") as a control. It returns {fail, unable_to_match_altnames}.\n* For the IP-literal variant, issue a leaf with dNSName *.168.1.1 and call verify_cert_hostname(Cert, \"192.168.1.1\"). It returns {valid, \"192.168.1.1\"}.\n* To observe the full TLS path, serve the first certificate from ssl:listen/2 and connect with {verify, verify_peer}, the CA in cacerts, {verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}} and {server_name_indication, disable}. The handshake succeeds. With {server_name_indication, \"f.evil.example.net\"} instead, OTP 20.0 or later rejects the certificate with hostname_check_failed before ssl_verify_fun runs.", "supportingMedia": [{"type": "text/html", "value": "<ol>\n<li>Issue a leaf certificate whose only <code>subjectAltName</code> entry is <code>dNSName</code> <code>f*.example.net</code>, for example with <code>public_key:pkix_test_data/1</code>, and decode it with <code>public_key:pkix_decode_cert(Der, otp)</code>.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\")</code>. It returns <code>{valid, \"foo.example.net\"}</code>, as expected.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\")</code>. It returns <code>{valid, \"f.evil.example.net\"}</code> although the hostname spans two labels where the wildcard sits.</li>\n<li>Call <code>ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\")</code> as a control. It returns <code>{fail, unable_to_match_altnames}</code>.</li>\n<li>For the IP-literal variant, issue a leaf with <code>dNSName</code> <code>*.168.1.1</code> and call <code>verify_cert_hostname(Cert, \"192.168.1.1\")</code>. It returns <code>{valid, \"192.168.1.1\"}</code>.</li>\n<li>To observe the full TLS path, serve the first certificate from <code>ssl:listen/2</code> and connect with <code>{verify, verify_peer}</code>, the CA in <code>cacerts</code>, <code>{verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}}</code> and <code>{server_name_indication, disable}</code>. The handshake succeeds. With <code>{server_name_indication, \"f.evil.example.net\"}</code> instead, OTP 20.0 or later rejects the certificate with <code>hostname_check_failed</code> before ssl_verify_fun runs.</li>\n</ol>", "base64": false}, {"type": "text/markdown", "value": "1. Issue a leaf certificate whose only `subjectAltName` entry is `dNSName` `f*.example.net`, for example with `public_key:pkix_test_data/1`, and decode it with `public_key:pkix_decode_cert(Der, otp)`.\n2. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"foo.example.net\")`. It returns `{valid, \"foo.example.net\"}`, as expected.\n3. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"f.evil.example.net\")`. It returns `{valid, \"f.evil.example.net\"}` although the hostname spans two labels where the wildcard sits.\n4. Call `ssl_verify_hostname:verify_cert_hostname(Cert, \"a.b.example.net\")` as a control. It returns `{fail, unable_to_match_altnames}`.\n5. For the IP-literal variant, issue a leaf with `dNSName` `*.168.1.1` and call `verify_cert_hostname(Cert, \"192.168.1.1\")`. It returns `{valid, \"192.168.1.1\"}`.\n6. To observe the full TLS path, serve the first certificate from `ssl:listen/2` and connect with `{verify, verify_peer}`, the CA in `cacerts`, `{verify_fun, {fun ssl_verify_hostname:verify_fun/3, [{check_hostname, \"f.evil.example.net\"}]}}` and `{server_name_indication, disable}`. The handshake succeeds. With `{server_name_indication, \"f.evil.example.net\"}` instead, OTP 20.0 or later rejects the certificate with `hostname_check_failed` before ssl_verify_fun runs.", "base64": false}]}], "x_technicalAnalysis": [{"lang": "en", "value": "1. Identifier parsing. ssl_verify_hostname:try_match_hostname/2 strips trailing dots, tries an exact case-insensitive match, and otherwise calls parse_and_validate_wildcard_identifier/2. That function accepts an identifier with one * in the left-most label and at least two labels after it, and classifies it as SingleCharW when the label is exactly *.\n\n2. Whole-label wildcard, correct. For *.example.net the matcher compares the text after the * with the hostname from its first dot onward, so a.b.example.net fails because .b.example.net differs from .example.net.\n\n3. Partial-label wildcard, incorrect. For f*.example.net the SingleCharW branch is skipped. try_match_wildcard/4 then checks only that the hostname ends with .example.net and starts with f. Nothing checks the span consumed by the *, so f.evil.example.net and f.a.b.example.net pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The wildcard_not_in_a_label/2 guard only rejects internationalized xn-- labels and does not help.\n\n4. IP literals. The reference identifier is treated as a DNS name whatever its shape, so verify_cert_hostname/2 with hostname 192.168.1.1 matches a dNSName of *.168.1.1 through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's ssl converts an IP-literal string to an {ip, ...} reference that only matches iPAddress entries.\n\n5. Interaction with Erlang/OTP. When ssl_verify_hostname:verify_fun/3 is used as verify_fun, OTP 20.0 and later call ssl_certificate:validate/4 for valid_peer before the user fun. In the client role with server_name_indication set to a hostname, or with a peer IP from a socket upgrade, OTP runs public_key:pkix_verify_hostname/3 and hands the user fun {bad_cert, hostname_check_failed} instead of valid_peer, which ssl_verify_fun turns into {fail, ...}. OTP's default match function allows no wildcards, and its https match function (public_key:pkix_verify_hostname_match_fun/1) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with {server_name_indication, disable}, in the server role, on direct calls to verify_cert_hostname/2, or on OTP older than 20.0.", "supportingMedia": [{"type": "text/html", "value": "<p><strong>1. Identifier parsing.</strong> <code>ssl_verify_hostname:try_match_hostname/2</code> strips trailing dots, tries an exact case-insensitive match, and otherwise calls <code>parse_and_validate_wildcard_identifier/2</code>. That function accepts an identifier with one <code>*</code> in the left-most label and at least two labels after it, and classifies it as <code>SingleCharW</code> when the label is exactly <code>*</code>.</p>\n<p><strong>2. Whole-label wildcard, correct.</strong> For <code>*.example.net</code> the matcher compares the text after the <code>*</code> with the hostname from its first dot onward, so <code>a.b.example.net</code> fails because <code>.b.example.net</code> differs from <code>.example.net</code>.</p>\n<p><strong>3. Partial-label wildcard, incorrect.</strong> For <code>f*.example.net</code> the <code>SingleCharW</code> branch is skipped. <code>try_match_wildcard/4</code> then checks only that the hostname ends with <code>.example.net</code> and starts with <code>f</code>. Nothing checks the span consumed by the <code>*</code>, so <code>f.evil.example.net</code> and <code>f.a.b.example.net</code> pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The <code>wildcard_not_in_a_label/2</code> guard only rejects internationalized <code>xn--</code> labels and does not help.</p>\n<p><strong>4. IP literals.</strong> The reference identifier is treated as a DNS name whatever its shape, so <code>verify_cert_hostname/2</code> with hostname <code>192.168.1.1</code> matches a <code>dNSName</code> of <code>*.168.1.1</code> through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's <code>ssl</code> converts an IP-literal string to an <code>{ip, ...}</code> reference that only matches <code>iPAddress</code> entries.</p>\n<p><strong>5. Interaction with Erlang/OTP.</strong> When <code>ssl_verify_hostname:verify_fun/3</code> is used as <code>verify_fun</code>, OTP 20.0 and later call <code>ssl_certificate:validate/4</code> for <code>valid_peer</code> before the user fun. In the client role with <code>server_name_indication</code> set to a hostname, or with a peer IP from a socket upgrade, OTP runs <code>public_key:pkix_verify_hostname/3</code> and hands the user fun <code>{bad_cert, hostname_check_failed}</code> instead of <code>valid_peer</code>, which ssl_verify_fun turns into <code>{fail, ...}</code>. OTP's default match function allows no wildcards, and its <code>https</code> match function (<code>public_key:pkix_verify_hostname_match_fun/1</code>) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with <code>{server_name_indication, disable}</code>, in the server role, on direct calls to <code>verify_cert_hostname/2</code>, or on OTP older than 20.0.</p>", "base64": false}, {"type": "text/markdown", "value": "**1. Identifier parsing.** `ssl_verify_hostname:try_match_hostname/2` strips trailing dots, tries an exact case-insensitive match, and otherwise calls `parse_and_validate_wildcard_identifier/2`. That function accepts an identifier with one `*` in the left-most label and at least two labels after it, and classifies it as `SingleCharW` when the label is exactly `*`.\n\n**2. Whole-label wildcard, correct.** For `*.example.net` the matcher compares the text after the `*` with the hostname from its first dot onward, so `a.b.example.net` fails because `.b.example.net` differs from `.example.net`.\n\n**3. Partial-label wildcard, incorrect.** For `f*.example.net` the `SingleCharW` branch is skipped. `try_match_wildcard/4` then checks only that the hostname ends with `.example.net` and starts with `f`. Nothing checks the span consumed by the `*`, so `f.evil.example.net` and `f.a.b.example.net` pass. RFC 6125 section 6.4.3 limits a wildcard to the left-most label. The `wildcard_not_in_a_label/2` guard only rejects internationalized `xn--` labels and does not help.\n\n**4. IP literals.** The reference identifier is treated as a DNS name whatever its shape, so `verify_cert_hostname/2` with hostname `192.168.1.1` matches a `dNSName` of `*.168.1.1` through the whole-label branch. RFC 6125 does not apply wildcard matching to IP addresses, and OTP's `ssl` converts an IP-literal string to an `{ip, ...}` reference that only matches `iPAddress` entries.\n\n**5. Interaction with Erlang/OTP.** When `ssl_verify_hostname:verify_fun/3` is used as `verify_fun`, OTP 20.0 and later call `ssl_certificate:validate/4` for `valid_peer` before the user fun. In the client role with `server_name_indication` set to a hostname, or with a peer IP from a socket upgrade, OTP runs `public_key:pkix_verify_hostname/3` and hands the user fun `{bad_cert, hostname_check_failed}` instead of `valid_peer`, which ssl_verify_fun turns into `{fail, ...}`. OTP's default match function allows no wildcards, and its `https` match function (`public_key:pkix_verify_hostname_match_fun/1`) splits both names on dots and matches the wildcard within the first label only. The ssl_verify_fun result therefore decides the outcome only with `{server_name_indication, disable}`, in the server role, on direct calls to `verify_cert_hostname/2`, or on OTP older than 20.0.", "base64": false}]}]}}, "cveMetadata": {"cveId": "CVE-2026-117666", "state": "PUBLISHED", "dateUpdated": "2026-11-06T16:02:49.781Z", "dateReserved": "2026-10-30T10:00:01.681Z", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "datePublished": "2026-10-30T20:22:16.466Z", "assignerShortName": "EEF"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["ssl_verify_hostname"], "packageName": "ssl_verify_fun", "packageURL": "pkg:hex/ssl_verify_fun", "product": "ssl_verify_fun", "programFiles": ["src/ssl_verify_hostname.erl"], "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "versions": [{"lessThan": "1.1.8", "status": "affected", "version": "1.0.1", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:deadtrickster:ssl_verify_fun:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["ssl_verify_hostname"], "packageName": "deadtrickster/ssl_verify_fun.erl", "packageURL": "pkg:github/deadtrickster/ssl_verify_fun.erl", "product": "ssl_verify_fun", "programFiles": ["src/ssl_verify_hostname.erl"], "programRoutines": [{"name": "ssl_verify_hostname:try_match_wildcard/4"}, {"name": "ssl_verify_hostname:try_match_hostname/2"}, {"name": "ssl_verify_hostname:verify_cert_hostname/2"}, {"name": "ssl_verify_hostname:verify_fun/3"}], "repo": "https://github.com/deadtrickster/ssl_verify_fun.erl", "vendor": "deadtrickster", "versions": [{"lessThan": "ca34031299cd2e0c98794c0da4ba556b94e39aad", "status": "affected", "version": "a49ca56923356c7a3981692b23c42ef32c2990e0", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. try_match_wildcard/4 in src/ssl_verify_hostname.erl anchors only the text before and after the * of an identifier such as f*.example.net, so the wildcard also consumes dots and the certificate is accepted for f.evil.example.net. RFC 6125 confines a wildcard to the left-most label. The same matcher lets *.168.1.1 match the IP literal 192.168.1.1. Whole-label wildcards are matched correctly.\n\nErlang/OTP 20.0 and later check the hostname in ssl before a user verify_fun sees valid_peer, so a client that keeps server_name_indication set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of verify_cert_hostname/2.\n\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8."}], "id": "CVE-2026-117666", "lastModified": "2026-11-06T16:17:49.210", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-117666", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-11-06T16:02:35.597989Z", "version": "2.0.3"}}]}, "published": "2026-10-30T21:16:51.447", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://cna.erlef.org/cves/CVE-2026-117666.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a3981692b23c42ef32c2990e0"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794c0da4ba556b94e39aad"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/pull/33"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw2-hphm-c5px"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://osv.dev/vulnerability/EEF-CVE-2026-117666"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-297"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

{"bugzilla": {"description": "ssl_verify_fun: ssl_verify_fun: partial-label wildcard certificate matches hostnames across a label boundary", "id": "2564302", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2564302"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.4", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N", "status": "draft"}, "cwe": "CWE-295", "details": ["Improper Validation of Certificate with Host Mismatch vulnerability in deadtrickster ssl_verify_fun allows an adversary in the middle to impersonate a TLS peer via a certificate that carries a partial-label wildcard. try_match_wildcard/4 in src/ssl_verify_hostname.erl anchors only the text before and after the * of an identifier such as f*.example.net, so the wildcard also consumes dots and the certificate is accepted for f.evil.example.net. RFC 6125 confines a wildcard to the left-most label. The same matcher lets *.168.1.1 match the IP literal 192.168.1.1. Whole-label wildcards are matched correctly.\nErlang/OTP 20.0 and later check the hostname in ssl before a user verify_fun sees valid_peer, so a client that keeps server_name_indication set rejects the mismatch regardless. Exposed are clients that disable SNI, servers that verify client certificate hostnames with this library, and direct callers of verify_cert_hostname/2.\nThis issue affects ssl_verify_fun: from 1.0.1 before 1.1.8.", "A flaw was found in ssl_verify_fun. The library improperly validates Transport Layer Security (TLS) certificates containing partial wildcards, allowing wildcard patterns to match across domain label boundaries and IP addresses. A man-in-the-middle attacker can exploit this vulnerability by presenting a crafted certificate for an unauthorized domain. Successful exploitation allows the attacker to impersonate a legitimate peer and intercept or tamper with encrypted communications."], "mitigation": {"lang": "en:us", "value": "Ensure Server Name Indication (SNI) remains enabled on TLS clients running Erlang/OTP 20.0 or later so built-in OTP hostname checks reject mismatches prior to ssl_verify_fun evaluation. Avoid issuing or accepting certificates with partial-label wildcards, and do not invoke verify_cert_hostname/2 directly on untrusted inputs without prior label boundary sanitization."}, "name": "CVE-2026-117666", "public_date": "2026-10-30T20:22:16Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-117666\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-117666\nhttps://cna.erlef.org/cves/CVE-2026-117666.html\nhttps://github.com/deadtrickster/ssl_verify_fun.erl/commit/a49ca56923356c7a3981692b23c42ef32c2990e0\nhttps://github.com/deadtrickster/ssl_verify_fun.erl/commit/ca34031299cd2e0c98794c0da4ba556b94e39aad\nhttps://github.com/deadtrickster/ssl_verify_fun.erl/pull/33\nhttps://github.com/deadtrickster/ssl_verify_fun.erl/security/advisories/GHSA-7gw2-hphm-c5px\nhttps://osv.dev/vulnerability/EEF-CVE-2026-117666"], "statement": "A flaw was found in the ssl_verify_fun library's try_match_wildcard/4 function within src/ssl_verify_hostname.erl. The wildcard matching logic improperly anchors only characters immediately before and after the asterisk, allowing wildcards to span domain label boundaries (dot characters) and match arbitrary IP literals. An attacker in an on-path / man-in-the-middle network position can exploit this behavior by presenting a certificate with a partial-label wildcard to bypass hostname verification and impersonate a legitimate TLS peer.", "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.0.1,1.1.8)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "ssl_verify_fun", "source": "cna", "vendor": "deadtrickster"}, "product": "ssl_verify_fun", "vendor": "deadtrickster"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[a49ca56923356c7a3981692b23c42ef32c2990e0,ca34031299cd2e0c98794c0da4ba556b94e39aad)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "ssl_verify_fun", "source": "cna", "vendor": "deadtrickster"}, "product": "ssl_verify_fun", "vendor": "deadtrickster"}], "created": "2026-10-30T21:45:15.223314+00:00", "updated": "2026-11-04T10:45:12.287013+00:00", "vendors": ["deadtrickster", "deadtrickster$PRODUCT$ssl_verify_fun"]}