{"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":"0.1.0","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":"7201270c34b90f6c9e15c0386c2bb802c0c72ab4","versionType":"git"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*","versionEndExcluding":"1.14.0","versionStartIncluding":"0.1.0","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":"2026-10-23T12:35:54.000Z","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks.

\n

The chunked reader in lib/bandit/http1/socket.ex keeps every chunk as its own list cell and binary term until IO.iodata_to_binary/1 joins them, and nothing limits the number of chunks. The :length option of read_body/2 counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections ensure_completed/1 drains unread bodies through the same reader.

\n

This issue affects bandit: from 0.1.0 before 1.14.0.

"},{"base64":false,"type":"text/markdown","value":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks.\n\nThe chunked reader in `lib/bandit/http1/socket.ex` keeps every chunk as its own list cell and binary term until `IO.iodata_to_binary/1` joins them, and nothing limits the number of chunks. The `:length` option of `read_body/2` counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections `ensure_completed/1` drains unread bodies through the same reader.\n\nThis issue affects bandit: from 0.1.0 before 1.14.0."}],"value":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/1.1 chunked body reader of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory and CPU via a request body made of many 1-byte chunks.\n\nThe chunked reader in lib/bandit/http1/socket.ex keeps every chunk as its own list cell and binary term until IO.iodata_to_binary/1 joins them, and nothing limits the number of chunks. The :length option of read_body/2 counts only data bytes, so tiny chunks cost far more memory than their payload: 48 MB of 1-byte chunks grew one handler process to about 500 MB and took about 6 s of CPU. The route does not need to read the body, because on keep-alive connections ensure_completed/1 drains unread bodies through the same reader.\n\nThis issue affects bandit: from 0.1.0 before 1.14.0."}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

An unauthenticated client can make a single HTTP/1.1 request hold many times its body size in server memory (about 48 MB for a 1 MB body in the reporter's test), and keep CPU busy while the chunks are joined. This affects any Bandit server that accepts HTTP/1.1 requests, whether or not its routes read the body.

"},{"base64":false,"type":"text/markdown","value":"An unauthenticated client can make a single HTTP/1.1 request hold many times its body size in server memory (about 48 MB for a 1 MB body in the reporter's test), and keep CPU busy while the chunks are joined. This affects any Bandit server that accepts HTTP/1.1 requests, whether or not its routes read the body."}],"value":"An unauthenticated client can make a single HTTP/1.1 request hold many times its body size in server memory (about 48 MB for a 1 MB body in the reporter's test), and keep CPU busy while the chunks are joined. This affects any Bandit server that accepts HTTP/1.1 requests, whether or not its routes read the body."}]}],"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-770","description":"CWE-770 Allocation of Resources Without Limits or Throttling","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-26T13:31:48.184Z","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","shortName":"EEF"},"references":[{"name":"HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in Bandit","tags":["vendor-advisory","related"],"url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-jwh3-j29h-qfmw"},{"name":"EEF CNA record for CVE-2026-111101","tags":["related"],"url":"https://cna.erlef.org/cves/CVE-2026-111101.html"},{"name":"OSV record EEF-CVE-2026-111101","tags":["related"],"url":"https://osv.dev/vulnerability/EEF-CVE-2026-111101"},{"name":"Introducing commit 7201270 in mtrudel/bandit","tags":["related"],"url":"https://github.com/mtrudel/bandit/commit/7201270c34b90f6c9e15c0386c2bb802c0c72ab4"},{"name":"Fix commit 220b9df in mtrudel/bandit","tags":["patch"],"url":"https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"}],"source":{"discovery":"UNKNOWN"},"title":"HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in Bandit","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

From 0.7.0, a server whose clients and proxies all speak HTTP/2 can disable HTTP/1 with http_1_options: [enabled: false], so that the vulnerable chunked body reader never runs.

"},{"base64":false,"type":"text/markdown","value":"From 0.7.0, a server whose clients and proxies all speak HTTP/2 can disable HTTP/1 with `http_1_options: [enabled: false]`, so that the vulnerable chunked body reader never runs."}],"value":"From 0.7.0, a server whose clients and proxies all speak HTTP/2 can disable HTTP/1 with http_1_options: [enabled: false], so that the vulnerable chunked body reader never runs."}],"x_proofOfConcept":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"
    \n
  1. Run Bandit with a Plug that calls Plug.Conn.read_body(conn, length: 1_000_000, read_length: 1_000_000).
    2. \n
  2. Send POST / with Transfer-Encoding: chunked and a body of 1,000,000 chunks of 1\\r\\nA\\r\\n, followed by 0\\r\\n\\r\\n.
    3. \n
  3. When read_body returns the 1,000,000 body bytes, the handler process holds about 48 MB and BEAM memory has grown by about 55 MB, for 6 MB sent.
    4. \n
"},{"base64":false,"type":"text/markdown","value":"1. Run Bandit with a Plug that calls `Plug.Conn.read_body(conn, length: 1_000_000, read_length: 1_000_000)`.\n2. Send `POST /` with `Transfer-Encoding: chunked` and a body of 1,000,000 chunks of `1\\r\\nA\\r\\n`, followed by `0\\r\\n\\r\\n`.\n3. When `read_body` returns the 1,000,000 body bytes, the handler process holds about 48 MB and BEAM memory has grown by about 55 MB, for 6 MB sent."}],"value":"* Run Bandit with a Plug that calls Plug.Conn.read_body(conn, length: 1_000_000, read_length: 1_000_000).\n* Send POST / with Transfer-Encoding: chunked and a body of 1,000,000 chunks of 1\\r\\nA\\r\\n, followed by 0\\r\\n\\r\\n.\n* When read_body returns the 1,000,000 body bytes, the handler process holds about 48 MB and BEAM memory has grown by about 55 MB, for 6 MB sent."}],"x_technicalAnalysis":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

1. Per-chunk accumulation. do_read_chunked_data! in lib/bandit/http1/socket.ex collects chunks as [body | chunk], adding a cons cell and a binary term for every chunk.

\n

2. Byte-only limit. :length limits data bytes, not the number of chunks, so a body of 1\\r\\nx\\r\\n chunks becomes an 8-million-element improper list before IO.iodata_to_binary runs. Sending 48 MB of 1-byte chunks grew the handler heap to about 500 MB and used about 6 s of CPU. The same body as one 8 MB chunk peaked at about 16 MB and took 5 ms.

\n

3. No body read needed. On keep-alive connections, ensure_completed/1 drains unread bodies through the same path. Against a Plug that never calls read_body, the attack used about 417 MB.

"},{"base64":false,"type":"text/markdown","value":"**1. Per-chunk accumulation.** `do_read_chunked_data!` in `lib/bandit/http1/socket.ex` collects chunks as `[body | chunk]`, adding a cons cell and a binary term for every chunk.\n\n**2. Byte-only limit.** `:length` limits data bytes, not the number of chunks, so a body of `1\\r\\nx\\r\\n` chunks becomes an 8-million-element improper list before `IO.iodata_to_binary` runs. Sending 48 MB of 1-byte chunks grew the handler heap to about 500 MB and used about 6 s of CPU. The same body as one 8 MB chunk peaked at about 16 MB and took 5 ms.\n\n**3. No body read needed.** On keep-alive connections, `ensure_completed/1` drains unread bodies through the same path. Against a Plug that never calls `read_body`, the attack used about 417 MB."}],"value":"1. Per-chunk accumulation. do_read_chunked_data! in lib/bandit/http1/socket.ex collects chunks as [body | chunk], adding a cons cell and a binary term for every chunk.\n\n2. Byte-only limit. :length limits data bytes, not the number of chunks, so a body of 1\\r\\nx\\r\\n chunks becomes an 8-million-element improper list before IO.iodata_to_binary runs. Sending 48 MB of 1-byte chunks grew the handler heap to about 500 MB and used about 6 s of CPU. The same body as one 8 MB chunk peaked at about 16 MB and took 5 ms.\n\n3. No body read needed. On keep-alive connections, ensure_completed/1 drains unread bodies through the same path. Against a Plug that never calls read_body, the attack used about 417 MB."}]}},"cveMetadata":{"assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","assignerShortName":"EEF","cveId":"CVE-2026-111101","datePublished":"2026-10-26T13:31:48.184Z","dateReserved":"2026-10-23T12:30:01.834Z","dateUpdated":"2026-10-26T13:31:48.184Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"}