CVE-2026-113436

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It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.</p>\n<p>This issue affects bandit: from 1.0.0-pre.7 before 1.14.0.</p>"}, {"base64": false, "type": "text/markdown", "value": "Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a `content-length` value or a `Host` or `:authority` port made of thousands of digits.\n\n`Bandit.Headers.parse_integer/2` in `lib/bandit/headers.ex` builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.\n\nThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0."}], "value": "Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a content-length value or a Host or :authority port made of thousands of digits.\n\nBandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.\n\nThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>An unauthenticated client can make the server spend CPU time out of all proportion to the traffic it sends (27.9 s for 124 KB in the reporter's test). This affects any Bandit server reachable by untrusted clients over HTTP/1 or HTTP/2, with no special configuration.</p>"}, {"base64": false, "type": "text/markdown", "value": "An unauthenticated client can make the server spend CPU time out of all proportion to the traffic it sends (27.9 s for 124 KB in the reporter's test). This affects any Bandit server reachable by untrusted clients over HTTP/1 or HTTP/2, with no special configuration."}], "value": "An unauthenticated client can make the server spend CPU time out of all proportion to the traffic it sends (27.9 s for 124 KB in the reporter's test). 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Run Bandit with any Plug.\n2. Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.\n3. In one write, send 5,000 HEADERS frames for `POST /` on new streams, each carrying a `content-length` of 4,000 `9` digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.\n4. The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug."}], "value": "* Run Bandit with any Plug.\n* Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.\n* In one write, send 5,000 HEADERS frames for POST / on new streams, each carrying a content-length of 4,000 9 digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.\n* The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug."}], "x_technicalAnalysis": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p><strong>1. Unbounded digit loop.</strong> <code>Bandit.Headers.parse_integer/2</code> in <code>lib/bandit/headers.ex</code> builds the number with <code>total * 10 + digit - ?0</code> and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where <code>String.to_integer/1</code> handles the same inputs in 1 to 3 ms.</p>\n<p><strong>2. Reached on raw input.</strong> It is called from <code>get_content_length/1</code> and <code>parse_hostlike_header!/1</code> on raw request input, before any range check. An all-digit <code>content-length</code> is returned as <code>{:ok, huge_int}</code>, and the <code>is_port_number</code> guard only runs after the whole number is built.</p>\n<p><strong>3. HPACK amplification.</strong> Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte.</p>"}, {"base64": false, "type": "text/markdown", "value": "**1. Unbounded digit loop.** `Bandit.Headers.parse_integer/2` in `lib/bandit/headers.ex` builds the number with `total * 10 + digit - ?0` and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where `String.to_integer/1` handles the same inputs in 1 to 3 ms.\n\n**2. Reached on raw input.** It is called from `get_content_length/1` and `parse_hostlike_header!/1` on raw request input, before any range check. An all-digit `content-length` is returned as `{:ok, huge_int}`, and the `is_port_number` guard only runs after the whole number is built.\n\n**3. HPACK amplification.** Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte."}], "value": "1. Unbounded digit loop. Bandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number with total * 10 + digit - ?0 and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where String.to_integer/1 handles the same inputs in 1 to 3 ms.\n\n2. Reached on raw input. It is called from get_content_length/1 and parse_hostlike_header!/1 on raw request input, before any range check. An all-digit content-length is returned as {:ok, huge_int}, and the is_port_number guard only runs after the whole number is built.\n\n3. HPACK amplification. Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte."}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-113436", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-26T15:12:04.626946Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-26T15:35:51.556Z"}}]}}

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It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.\n\nThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0.", "supportingMedia": [{"type": "text/html", "value": "<p>Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a <code>content-length</code> value or a <code>Host</code> or <code>:authority</code> port made of thousands of digits.</p>\n<p><code>Bandit.Headers.parse_integer/2</code> in <code>lib/bandit/headers.ex</code> builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.</p>\n<p>This issue affects bandit: from 1.0.0-pre.7 before 1.14.0.</p>", "base64": false}, {"type": "text/markdown", "value": "Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a `content-length` value or a `Host` or `:authority` port made of thousands of digits.\n\n`Bandit.Headers.parse_integer/2` in `lib/bandit/headers.ex` builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.\n\nThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-407", "description": "CWE-407 Inefficient Algorithmic Complexity"}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.14.0", "versionStartIncluding": "1.0.0-pre.7"}], "operator": "OR"}], "operator": "AND"}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-10-26T13:31:35.033Z"}, "x_proofOfConcept": [{"lang": "en", "value": "* Run Bandit with any Plug.\n* Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.\n* In one write, send 5,000 HEADERS frames for POST / on new streams, each carrying a content-length of 4,000 9 digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.\n* The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug.", "supportingMedia": [{"type": "text/html", "value": "<ol>\n<li>Run Bandit with any Plug.</li>\n<li>Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.</li>\n<li>In one write, send 5,000 HEADERS frames for <code>POST /</code> on new streams, each carrying a <code>content-length</code> of 4,000 <code>9</code> digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.</li>\n<li>The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug.</li>\n</ol>", "base64": false}, {"type": "text/markdown", "value": "1. Run Bandit with any Plug.\n2. Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.\n3. In one write, send 5,000 HEADERS frames for `POST /` on new streams, each carrying a `content-length` of 4,000 `9` digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.\n4. The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug.", "base64": false}]}], "x_technicalAnalysis": [{"lang": "en", "value": "1. Unbounded digit loop. Bandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number with total * 10 + digit - ?0 and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where String.to_integer/1 handles the same inputs in 1 to 3 ms.\n\n2. Reached on raw input. It is called from get_content_length/1 and parse_hostlike_header!/1 on raw request input, before any range check. An all-digit content-length is returned as {:ok, huge_int}, and the is_port_number guard only runs after the whole number is built.\n\n3. HPACK amplification. Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte.", "supportingMedia": [{"type": "text/html", "value": "<p><strong>1. Unbounded digit loop.</strong> <code>Bandit.Headers.parse_integer/2</code> in <code>lib/bandit/headers.ex</code> builds the number with <code>total * 10 + digit - ?0</code> and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where <code>String.to_integer/1</code> handles the same inputs in 1 to 3 ms.</p>\n<p><strong>2. Reached on raw input.</strong> It is called from <code>get_content_length/1</code> and <code>parse_hostlike_header!/1</code> on raw request input, before any range check. An all-digit <code>content-length</code> is returned as <code>{:ok, huge_int}</code>, and the <code>is_port_number</code> guard only runs after the whole number is built.</p>\n<p><strong>3. HPACK amplification.</strong> Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte.</p>", "base64": false}, {"type": "text/markdown", "value": "**1. Unbounded digit loop.** `Bandit.Headers.parse_integer/2` in `lib/bandit/headers.ex` builds the number with `total * 10 + digit - ?0` and has no limit on the digit count. Each step allocates a new bignum, so parsing one value costs O(n\u00b2). On OTP 28, 10,000 digits take about 10 ms, 50,000 about 250 ms and 80,000 about 560 ms, where `String.to_integer/1` handles the same inputs in 1 to 3 ms.\n\n**2. Reached on raw input.** It is called from `get_content_length/1` and `parse_hostlike_header!/1` on raw request input, before any range check. An all-digit `content-length` is returned as `{:ok, huge_int}`, and the `is_port_number` guard only runs after the whole number is built.\n\n**3. HPACK amplification.** Over HTTP/2, a 4,000-digit value (about 1.1 ms to parse) can be stored once in the HPACK dynamic table and then re-sent on each new stream for about one byte.", "base64": false}]}]}}, "cveMetadata": {"cveId": "CVE-2026-113436", "state": "PUBLISHED", "dateUpdated": "2026-10-26T15:35:51.556Z", "dateReserved": "2026-10-23T10:30:01.881Z", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "datePublished": "2026-10-26T13:31:35.033Z", "assignerShortName": "EEF"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "bandit", "packageURL": "pkg:hex/bandit", "product": "bandit", "repo": "https://github.com/mtrudel/bandit", "vendor": "mtrudel", "versions": [{"lessThan": "1.14.0", "status": "affected", "version": "1.0.0-pre.7", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "mtrudel/bandit", "packageURL": "pkg:github/mtrudel/bandit", "product": "bandit", "repo": "https://github.com/mtrudel/bandit", "vendor": "mtrudel", "versions": [{"lessThan": "220b9dfd27f9a21305be2afc75cbe585ddc24e7a", "status": "affected", "version": "e0c8c0c30af9b0f57d8aafac37ddd9294363a8be", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Inefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a content-length value or a Host or :authority port made of thousands of digits.\n\nBandit.Headers.parse_integer/2 in lib/bandit/headers.ex builds the number one digit at a time with no limit on the digit count, allocating a new bignum at each step, so one value costs time quadratic in its length. It runs on raw request input over HTTP/1 and HTTP/2, before any range check. Over HTTP/2, a 4,000-digit value can be stored once in the HPACK dynamic table and re-sent on each new stream for about one byte: 124 KB of traffic kept the server busy for 27.9 s.\n\nThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0."}], "id": "CVE-2026-113436", "lastModified": "2026-10-26T16:59:16.113", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.7, "baseSeverity": "HIGH", "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:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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": "HIGH", "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-2026-113436", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-10-26T15:12:04.626946Z", "version": "2.0.3"}}]}, "published": "2026-10-26T14:16:28.680", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://cna.erlef.org/cves/CVE-2026-113436.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/mtrudel/bandit/commit/e0c8c0c30af9b0f57d8aafac37ddd9294363a8be"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-29cr-8477-rg6r"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://osv.dev/vulnerability/EEF-CVE-2026-113436"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-407"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.0.0-pre.7,1.14.0)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "bandit", "source": "cna", "vendor": "mtrudel"}, "product": "bandit", "vendor": "mtrudel"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[e0c8c0c30af9b0f57d8aafac37ddd9294363a8be,220b9dfd27f9a21305be2afc75cbe585ddc24e7a)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "bandit", "source": "cna", "vendor": "mtrudel"}, "product": "bandit", "vendor": "mtrudel"}], "created": "2026-10-26T16:00:18.060030+00:00", "updated": "2026-10-26T16:15:14.281731+00:00", "vendors": ["mtrudel", "mtrudel$PRODUCT$bandit"]}