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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\": \"\u003cp\u003eInefficient Algorithmic Complexity vulnerability in the header integer parser of mtrudel bandit allows an unauthenticated remote attacker to consume server CPU via a \u003ccode\u003econtent-length\u003c/code\u003e value or a \u003ccode\u003eHost\u003c/code\u003e or \u003ccode\u003e:authority\u003c/code\u003e port made of thousands of digits.\u003c/p\u003e\\n\u003cp\u003e\u003ccode\u003eBandit.Headers.parse_integer/2\u003c/code\u003e in \u003ccode\u003elib/bandit/headers.ex\u003c/code\u003e 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.\u003c/p\u003e\\n\u003cp\u003eThis issue affects bandit: from 1.0.0-pre.7 before 1.14.0.\u003c/p\u003e\", \"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\": \"\u003col\u003e\\n\u003cli\u003eRun Bandit with any Plug.\u003c/li\u003e\\n\u003cli\u003eOpen an HTTP/2 connection with prior knowledge and complete the SETTINGS exchange.\u003c/li\u003e\\n\u003cli\u003eIn one write, send 5,000 HEADERS frames for \u003ccode\u003ePOST /\u003c/code\u003e on new streams, each carrying a \u003ccode\u003econtent-length\u003c/code\u003e of 4,000 \u003ccode\u003e9\u003c/code\u003e digits encoded with HPACK indexing, so that every frame after the first refers to the stored value.\u003c/li\u003e\\n\u003cli\u003eThe 124,003 bytes take 27.9 s to process before all 5,000 requests reach the Plug.\u003c/li\u003e\\n\u003c/ol\u003e\", \"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\": \"\u003cp\u003e\u003cstrong\u003e1. Unbounded digit loop.\u003c/strong\u003e \u003ccode\u003eBandit.Headers.parse_integer/2\u003c/code\u003e in \u003ccode\u003elib/bandit/headers.ex\u003c/code\u003e builds the number with \u003ccode\u003etotal * 10 + digit - ?0\u003c/code\u003e 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 \u003ccode\u003eString.to_integer/1\u003c/code\u003e handles the same inputs in 1 to 3 ms.\u003c/p\u003e\\n\u003cp\u003e\u003cstrong\u003e2. Reached on raw input.\u003c/strong\u003e It is called from \u003ccode\u003eget_content_length/1\u003c/code\u003e and \u003ccode\u003eparse_hostlike_header!/1\u003c/code\u003e on raw request input, before any range check. An all-digit \u003ccode\u003econtent-length\u003c/code\u003e is returned as \u003ccode\u003e{:ok, huge_int}\u003c/code\u003e, and the \u003ccode\u003eis_port_number\u003c/code\u003e guard only runs after the whole number is built.\u003c/p\u003e\\n\u003cp\u003e\u003cstrong\u003e3. HPACK amplification.\u003c/strong\u003e 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.\u003c/p\u003e\", \"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\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}