{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-113436", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-10-23T10:30:01.881Z", "datePublished": "2026-10-26T13:31:35.033Z", "dateUpdated": "2026-10-26T15:35:51.556Z" }, "containers": { "cna": { "affected": [ { "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" } ] } ], "cpeApplicability": [ { "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.14.0", "versionStartIncluding": "1.0.0-pre.7", "vulnerable": true } ], "negate": false, "operator": "OR" } ], "operator": "AND" } ], "credits": [ { "lang": "en", "type": "reporter", "value": "Peter Ullrich" }, { "lang": "en", "type": "remediation developer", "value": "Mat Trudel" }, { "lang": "en", "type": "analyst", "value": "Jonatan Männchen / EEF" } ], "dateAssigned": "2026-10-23T12:44:41.000Z", "descriptions": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "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

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

This issue affects bandit: from 1.0.0-pre.7 before 1.14.0.

" }, { "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": "

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.

" }, { "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). This affects any Bandit server reachable by untrusted clients over HTTP/1 or HTTP/2, with no special configuration." } ] } ], "metrics": [ { "cvssV4_0": { "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 8.7, "baseSeverity": "HIGH", "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", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED" }, "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ] } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-407", "description": "CWE-407 Inefficient Algorithmic Complexity", "lang": "en", "type": "CWE" } ] } ], "providerMetadata": { "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-10-26T13:31:35.033Z" }, "references": [ { "name": "Quadratic bignum parsing of Content-Length and Host port values in Bandit", "tags": [ "vendor-advisory", "related" ], "url": "https://github.com/mtrudel/bandit/security/advisories/GHSA-29cr-8477-rg6r" }, { "name": "EEF CNA record for CVE-2026-113436", "tags": [ "related" ], "url": "https://cna.erlef.org/cves/CVE-2026-113436.html" }, { "name": "OSV record EEF-CVE-2026-113436", "tags": [ "related" ], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-113436" }, { "name": "Introducing commit e0c8c0c in mtrudel/bandit", "tags": [ "related" ], "url": "https://github.com/mtrudel/bandit/commit/e0c8c0c30af9b0f57d8aafac37ddd9294363a8be" }, { "name": "Fix commit 220b9df in mtrudel/bandit", "tags": [ "patch" ], "url": "https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a" } ], "source": { "discovery": "UNKNOWN" }, "title": "Quadratic bignum parsing of Content-Length and Host port values in Bandit", "x_proofOfConcept": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "value": "
    \n
  1. Run Bandit with any Plug.
    2. \n
  2. Open an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.
    3. \n
  3. 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.
    4. \n
  4. The 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug.
    5. \n
" }, { "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." } ], "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": "

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(n²). 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

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

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, "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(n²). 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(n²). 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" } } ] } }