CVE-2026-43966

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-43966", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-05-04T18:23:25.573Z", "datePublished": "2026-06-08T16:34:33.364Z", "dateUpdated": "2026-11-09T15:27:41.487Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["cow_http_struct_hd"], "packageName": "cowlib", "packageURL": "pkg:hex/cowlib", "product": "cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "versions": [{"lessThan": "2.22.0", "status": "affected", "version": "2.9.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["cow_http_struct_hd"], "packageName": "ninenines/cowlib", "packageURL": "pkg:github/ninenines/cowlib", "product": "cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "versions": [{"lessThan": "4401b858f2229abb3ea115c60924f6c77e5f8aa3", "status": "affected", "version": "a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The application must pass attacker-controlled data as a string value into <code>cow_http_struct_hd:item/1</code> (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected.</p>"}, {"base64": false, "type": "text/markdown", "value": "The application must pass attacker-controlled data as a string value into `cow_http_struct_hd:item/1` (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected."}], "value": "The application must pass attacker-controlled data as a string value into cow_http_struct_hd:item/1 (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.22.0", "versionStartIncluding": "2.9.0", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "Lo\u00efc Hoguin"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "datePublic": "2026-10-14T09:20:41.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.</p>\n<p><code>cow_http_struct_hd:escape_string/2</code> in cowlib only escapes <code>\\</code> and <code>\"</code>, passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding <code>\"</code> and <code>\\</code>), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via <code>cow_http_struct_hd:item/1</code> (or a higher-level wrapper such as <code>cow_http_hd:wt_protocol/1</code>) from attacker-controlled input can have <code>\\r\\n</code> injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.</p>\n<p>This issue affects cowlib: from 2.9.0 before 2.22.0.</p>"}, {"base64": false, "type": "text/markdown", "value": "Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\n`cow_http_struct_hd:escape_string/2` in cowlib only escapes `\\` and `\"`, passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding `\"` and `\\`), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via `cow_http_struct_hd:item/1` (or a higher-level wrapper such as `cow_http_hd:wt_protocol/1`) from attacker-controlled input can have `\\r\\n` injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 before 2.22.0."}], "value": "Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\ncow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 before 2.22.0."}], "impacts": [{"capecId": "CAPEC-34", "descriptions": [{"lang": "en", "value": "CAPEC-34 HTTP Response Splitting"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 6.3, "baseSeverity": "MEDIUM", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-113", "description": "CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-11-09T15:27:41.487Z"}, "references": [{"name": "cowboy: Add invalid_response_headers HTTP/1 option", "tags": ["mitigation"], "url": "https://github.com/ninenines/cowboy/commit/f77cb9b5e730e300fffb551db1ba5d1c4ed878ef"}, {"name": "EEF CNA record for CVE-2026-43966", "tags": ["related", "third-party-advisory"], "url": "https://cna.erlef.org/cves/CVE-2026-43966.html"}, {"name": "OSV record EEF-CVE-2026-43966", "tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-43966"}, {"name": "gun: Add invalid_request_headers request option", "tags": ["mitigation"], "url": "https://github.com/ninenines/gun/commit/4f35609eb37109b106a863fc9ba83d7ee64e3e42"}, {"name": "Introducing commit a8b793d in ninenines/cowlib", "tags": ["related"], "url": "https://github.com/ninenines/cowlib/commit/a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6"}, {"name": "Fix commit 4401b85 in ninenines/cowlib", "tags": ["patch"], "url": "https://github.com/ninenines/cowlib/commit/4401b858f2229abb3ea115c60924f6c77e5f8aa3"}], "source": {"discovery": "EXTERNAL"}, "title": "HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Validate all values passed into structured-fields header builders (directly via <code>cow_http_struct_hd:item/1</code> or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (<code>\\r</code>) or LF (<code>\\n</code>) bytes.</p>\n<p>Applications using cowboy 2.16.0 or later are protected on the server side by the <code>invalid_response_headers</code> option (defaults to <code>error_terminate</code>), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the <code>invalid_request_headers</code> request option (defaults to <code>raise</code>), which raises an exception when an outgoing request header value contains CR or LF.</p>"}, {"base64": false, "type": "text/markdown", "value": "Validate all values passed into structured-fields header builders (directly via `cow_http_struct_hd:item/1` or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (`\\r`) or LF (`\\n`) bytes.\n\nApplications using cowboy 2.16.0 or later are protected on the server side by the `invalid_response_headers` option (defaults to `error_terminate`), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the `invalid_request_headers` request option (defaults to `raise`), which raises an exception when an outgoing request header value contains CR or LF."}], "value": "Validate all values passed into structured-fields header builders (directly via cow_http_struct_hd:item/1 or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (\\r) or LF (\\n) bytes.\n\nApplications using cowboy 2.16.0 or later are protected on the server side by the invalid_response_headers option (defaults to error_terminate), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the invalid_request_headers request option (defaults to raise), which raises an exception when an outgoing request header value contains CR or LF."}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-06-08T18:37:59.853576Z", "id": "CVE-2026-43966", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-06-08T18:38:08.160Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-43966", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-06-08T18:37:59.853576Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-06-08T18:38:04.203Z"}}], "cna": {"title": "HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "Lo\u00efc Hoguin"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "impacts": [{"capecId": "CAPEC-34", "descriptions": [{"lang": "en", "value": "CAPEC-34 HTTP Response Splitting"}]}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 6.3, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "subIntegrityImpact": "LOW", "vulnIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "modules": ["cow_http_struct_hd"], "product": "cowlib", "versions": [{"status": "affected", "version": "2.9.0", "lessThan": "2.22.0", "versionType": "semver"}], "packageURL": "pkg:hex/cowlib", "packageName": "cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "collectionURL": "https://repo.hex.pm", "defaultStatus": "unaffected", "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}]}, {"cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "modules": ["cow_http_struct_hd"], "product": "cowlib", "versions": [{"status": "affected", "version": "a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6", "lessThan": "4401b858f2229abb3ea115c60924f6c77e5f8aa3", "versionType": "git"}], "packageURL": "pkg:github/ninenines/cowlib", "packageName": "ninenines/cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "collectionURL": "https://github.com", "defaultStatus": "unaffected", "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}]}], "datePublic": "2026-10-14T09:20:41.000Z", "references": [{"url": "https://github.com/ninenines/cowboy/commit/f77cb9b5e730e300fffb551db1ba5d1c4ed878ef", "name": "cowboy: Add invalid_response_headers HTTP/1 option", "tags": ["mitigation"]}, {"url": "https://cna.erlef.org/cves/CVE-2026-43966.html", "name": "EEF CNA record for CVE-2026-43966", "tags": ["related", "third-party-advisory"]}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-43966", "name": "OSV record EEF-CVE-2026-43966", "tags": ["related"]}, {"url": "https://github.com/ninenines/gun/commit/4f35609eb37109b106a863fc9ba83d7ee64e3e42", "name": "gun: Add invalid_request_headers request option", "tags": ["mitigation"]}, {"url": "https://github.com/ninenines/cowlib/commit/a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6", "name": "Introducing commit a8b793d in ninenines/cowlib", "tags": ["related"]}, {"url": "https://github.com/ninenines/cowlib/commit/4401b858f2229abb3ea115c60924f6c77e5f8aa3", "name": "Fix commit 4401b85 in ninenines/cowlib", "tags": ["patch"]}], "workarounds": [{"lang": "en", "value": "Validate all values passed into structured-fields header builders (directly via cow_http_struct_hd:item/1 or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (\\r) or LF (\\n) bytes.\n\nApplications using cowboy 2.16.0 or later are protected on the server side by the invalid_response_headers option (defaults to error_terminate), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the invalid_request_headers request option (defaults to raise), which raises an exception when an outgoing request header value contains CR or LF.", "supportingMedia": [{"type": "text/html", "value": "<p>Validate all values passed into structured-fields header builders (directly via <code>cow_http_struct_hd:item/1</code> or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (<code>\\r</code>) or LF (<code>\\n</code>) bytes.</p>\n<p>Applications using cowboy 2.16.0 or later are protected on the server side by the <code>invalid_response_headers</code> option (defaults to <code>error_terminate</code>), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the <code>invalid_request_headers</code> request option (defaults to <code>raise</code>), which raises an exception when an outgoing request header value contains CR or LF.</p>", "base64": false}, {"type": "text/markdown", "value": "Validate all values passed into structured-fields header builders (directly via `cow_http_struct_hd:item/1` or indirectly via higher-level wrappers) before calling the encoder. Reject any value that is not from a trusted, application-controlled source or that contains CR (`\\r`) or LF (`\\n`) bytes.\n\nApplications using cowboy 2.16.0 or later are protected on the server side by the `invalid_response_headers` option (defaults to `error_terminate`), which rejects any outgoing response header value containing CR or LF before it reaches the wire. Applications using gun 2.4.0 or later are protected on the client side by the `invalid_request_headers` request option (defaults to `raise`), which raises an exception when an outgoing request header value contains CR or LF.", "base64": false}]}], "descriptions": [{"lang": "en", "value": "Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\ncow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 before 2.22.0.", "supportingMedia": [{"type": "text/html", "value": "<p>Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.</p>\n<p><code>cow_http_struct_hd:escape_string/2</code> in cowlib only escapes <code>\\</code> and <code>\"</code>, passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding <code>\"</code> and <code>\\</code>), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via <code>cow_http_struct_hd:item/1</code> (or a higher-level wrapper such as <code>cow_http_hd:wt_protocol/1</code>) from attacker-controlled input can have <code>\\r\\n</code> injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.</p>\n<p>This issue affects cowlib: from 2.9.0 before 2.22.0.</p>", "base64": false}, {"type": "text/markdown", "value": "Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\n`cow_http_struct_hd:escape_string/2` in cowlib only escapes `\\` and `\"`, passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding `\"` and `\\`), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via `cow_http_struct_hd:item/1` (or a higher-level wrapper such as `cow_http_hd:wt_protocol/1`) from attacker-controlled input can have `\\r\\n` injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 before 2.22.0.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-113", "description": "CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers"}]}], "configurations": [{"lang": "en", "value": "The application must pass attacker-controlled data as a string value into cow_http_struct_hd:item/1 (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected.", "supportingMedia": [{"type": "text/html", "value": "<p>The application must pass attacker-controlled data as a string value into <code>cow_http_struct_hd:item/1</code> (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected.</p>", "base64": false}, {"type": "text/markdown", "value": "The application must pass attacker-controlled data as a string value into `cow_http_struct_hd:item/1` (or a wrapper that delegates to it). Applications that construct structured-fields header values exclusively from trusted, application-controlled values are not affected.", "base64": false}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "2.22.0", "versionStartIncluding": "2.9.0"}], "operator": "OR"}], "operator": "AND"}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-11-09T15:27:41.487Z"}}}, "cveMetadata": {"cveId": "CVE-2026-43966", "state": "PUBLISHED", "dateUpdated": "2026-11-09T15:27:41.487Z", "dateReserved": "2026-05-04T18:23:25.573Z", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "datePublished": "2026-06-08T16:34:33.364Z", "assignerShortName": "EEF"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["cow_http_struct_hd"], "packageName": "cowlib", "packageURL": "pkg:hex/cowlib", "product": "cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "versions": [{"lessThan": "2.22.0", "status": "affected", "version": "2.9.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["cow_http_struct_hd"], "packageName": "ninenines/cowlib", "packageURL": "pkg:github/ninenines/cowlib", "product": "cowlib", "programFiles": ["src/cow_http_struct_hd.erl"], "programRoutines": [{"name": "cow_http_struct_hd:escape_string/2"}, {"name": "cow_http_struct_hd:bare_item/1"}], "repo": "https://github.com/ninenines/cowlib", "vendor": "ninenines", "versions": [{"lessThan": "4401b858f2229abb3ea115c60924f6c77e5f8aa3", "status": "affected", "version": "a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*", "matchCriteriaId": "A583B546-6841-4B45-9E4D-67B1926640AB", "versionEndExcluding": "2.16.0", "versionStartIncluding": "2.9.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\ncow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 before 2.22.0."}, {"lang": "es", "value": "La vulnerabilidad de Neutralizaci\u00f3n Incorrecta de Secuencias CRLF en Encabezados HTTP ('Divisi\u00f3n de Solicitud/Respuesta HTTP') en ninenines cowlib permite la divisi\u00f3n de respuesta HTTP a trav\u00e9s de bytes no VCHAR en valores de cadena de campos estructurados.\n\ncow_http_struct_hd:escape_string/2 en cowlib solo escapa \\ y \", pasando todos los dem\u00e1s bytes textualmente. Esto crea una asimetr\u00eda de codificador/decodificador: el analizador coincidente acepta solo ASCII imprimible (0x20-0x7E, excluyendo \" y \\), pero el codificador emite cualquier byte, incluidos CR y LF. Una aplicaci\u00f3n que construye un encabezado HTTP estructurado a trav\u00e9s de cow_http_struct_hd:item/1 (o un envoltorio de nivel superior como cow_http_hd:wt_protocol/1) desde una entrada controlada por el atacante puede tener \\r\\n inyectado en el valor del encabezado serializado. Una vez en la red, el CRLF inyectado termina el encabezado actual y cualquier byte siguiente se interpreta como un nuevo encabezado, lo que permite la divisi\u00f3n de respuesta HTTP.\n\nEste problema afecta a cowlib desde la versi\u00f3n 2.9.0."}], "id": "CVE-2026-43966", "lastModified": "2026-11-09T16:17:33.340", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.3, "baseSeverity": "MEDIUM", "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": "LOW", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-43966", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-06-08T18:37:59.853576Z", "version": "2.0.3"}}]}, "published": "2026-06-08T17:16:43.447", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Third Party Advisory"], "url": "https://cna.erlef.org/cves/CVE-2026-43966.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/ninenines/cowboy/commit/f77cb9b5e730e300fffb551db1ba5d1c4ed878ef"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/ninenines/cowlib/commit/4401b858f2229abb3ea115c60924f6c77e5f8aa3"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/ninenines/cowlib/commit/a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/ninenines/gun/commit/4f35609eb37109b106a863fc9ba83d7ee64e3e42"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Third Party Advisory"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-43966"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-113"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.9.0"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "product": "cowlib", "vendor": "ninenines"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.9.0"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "cowlib", "source": "cna", "vendor": "ninenines"}, "product": "cowlib", "vendor": "ninenines"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "cowlib", "source": "cna", "vendor": "ninenines"}, "product": "cowlib", "vendor": "ninenines"}], "created": "2026-06-08T18:30:16.700531+00:00", "updated": "2026-11-09T17:15:07.075654+00:00", "vendors": ["ninenines", "ninenines$PRODUCT$cowlib"], "weaknesses": ["CWE-113"]}