{"id":"CVE-2026-115269","aliases":["EEF-CVE-2026-115269","EUVD-2026-109819","GHSA-p2qv-vx88-385x","UBUNTU-CVE-2026-115269"],"status":"published","title":"HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\nBandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.","severity":{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00602,"percentile":0.49332,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-770","CWE-835"],"published":"2026-10-26T13:30:24Z","modified":"2026-10-28T20:18:18Z","fixes":[{"ecosystem":"Hex","package":"bandit","fixed_in":["1.14.0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Hex","package":"bandit","ranges":[{"type":"SEMVER","events":[{"introduced":"1.4.0"},{"fixed":"1.14.0"}]}],"versions":["1.10.0","1.10.1","1.10.2","1.10.3","1.10.4","1.11.0","1.11.1","1.12.0","1.12.1","1.12.2","1.12.3","1.12.4","1.12.5","1.13.0","1.13.1","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.6.0","1.6.1","1.6.10","1.6.11","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.8.0","1.9.0"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.13.2-1","0.13.2-3"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.0-0ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.1-3","1.6.2-1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.6.2-1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.6.2-3"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.7.10-3","1.9.4-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"bandit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.7.10-2","1.7.10-3"]}],"products":[{"vendor":"mtrudel","product":"bandit"}],"references":[{"url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-p2qv-vx88-385x","tags":["vendor-advisory","related","advisory"]},{"url":"https://cna.erlef.org/cves/CVE-2026-115269.html","tags":["related","web"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-115269","tags":["related","web"]},{"url":"https://github.com/mtrudel/bandit/commit/fff06efe3be962b484bd4d3eb339372fda5a231f","tags":["related","fix","web","report"]},{"url":"https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a","tags":["patch","fix","report"]},{"url":"https://github.com","tags":["web","report"]},{"url":"https://repo.hex.pm","tags":["web","report"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/115xxx/CVE-2026-115269.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-115269","tags":["advisory"]},{"url":"https://github.com/mtrudel/bandit","tags":["package","report"]},{"url":"https://hex.pm/packages/bandit","tags":["package","report"]},{"url":"https://ubuntu.com/security/CVE-2026-115269","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-115269","tags":["report"]},{"url":"https://cna.erlef.org/cves/cve-2026-115269.html","tags":["report"]},{"url":"https://github.com/mtrudel/bandit/security/advisories/ghsa-p2qv-vx88-385x","tags":["report"]},{"url":"https://github.com/cveproject/cvelistv5/tree/main/cves/2026/115xxx/cve-2026-115269.json","tags":["report"]},{"url":"https://nvd.nist.gov/vuln/detail/cve-2026-115269","tags":["report"]},{"url":"https://osv.dev/vulnerability/eef-cve-2026-115269","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-115269","title":"HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\nBandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.","status":"published","published":"2026-10-26T13:30:24.621Z","modified":"2026-10-26T15:35:52.079Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna"}],"cwes":["CWE-835","CWE-770"],"updated_at":"2026-11-02T14:20:01.618694Z"}],"euvd":[{"id":"EUVD-2026-109819","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\nBandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.","status":"published","published":"2026-10-26T13:30:24Z","modified":"2026-10-26T15:35:52Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T16:59:29.561971Z"}],"nvd":[{"id":"CVE-2026-115269","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\nBandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.","status":"published","published":"2026-10-26T14:16:31.29Z","modified":"2026-10-26T16:59:16.113Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"secondary"}],"cwes":["CWE-770","CWE-835"],"updated_at":"2026-11-02T14:13:03.452847Z"}],"osv":[{"id":"CVE-2026-115269","title":"HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\nBandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.","status":"published","published":"2026-10-26T13:30:24.621Z","modified":"2026-10-28T02:56:13.90190005Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-770","CWE-835"],"updated_at":"2026-11-02T15:44:56.675758Z"},{"id":"EEF-CVE-2026-115269","title":"HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit","description":"## Summary\n\nAllocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body.\n\n`Bandit.HTTP2.Stream.do_read_data/4` in `lib/bandit/http2/stream.ex` waits for each frame with a fresh `read_timeout`. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps `read_body` blocked, together with the stream process and whatever the application holds while reading, for as long as it likes.\n\nThis issue affects bandit: from 1.4.0 before 1.14.0.\n\n## Details\n\n**1. Per-receive timeout.** `Bandit.HTTP2.Stream.read_data/2` passes a flat `read_timeout` (default 15,000 ms) to `do_read_data/4`, which blocks in `do_recv/2`'s `receive ... after timeout`.\n\n**2. Non-progress frames end the wait.** A stream WINDOW_UPDATE, delivered through `Bandit.HTTP2.Connection.handle_frame/3`, or an empty SETTINGS frame, which delivers a zero-delta window update to every stream, is matched inside that `receive`. `do_recv_send_window_update/2` returns a bare `%Stream{}`, and `do_read_data/4` recurses with the identical `timeout`, restarting the countdown.\n\n**3. Nothing else bounds the read.** The transport read timeout fires only when no bytes arrive, `max_bytes` is decremented only by DATA frames, and neither WINDOW_UPDATE nor SETTINGS frames are rate limited. The send path in `do_send_data/4` uses a progress-based deadline; the read path does not.\n\n## Proof of concept\n\n1. Run Bandit with a Plug that calls `Plug.Conn.read_body/2`.\n2. Open an HTTP/2 connection and send HEADERS for `POST /` on stream 1 without END_STREAM.\n3. Every 10 seconds, send a WINDOW_UPDATE on stream 1 with an increment of 1.\n4. The stream stays open for 120 s, eight times the default 15 s `read_timeout`. Without the WINDOW_UPDATE frames, the server ends the read after about 15 s.\n\n## Impact\n\nAn unauthenticated client can keep a Bandit HTTP/2 stream, and whatever its request handler holds while reading the body, occupied indefinitely for 9 bytes per `read_timeout`, and repeat this across many streams and connections. This affects any Bandit server with HTTP/2 enabled whose routes read request bodies, which `Plug.Parsers` does for POST, PUT and PATCH.\n\n## Workarounds\n\nDisable HTTP/2 with `http_2_options: [enabled: false]`, so that the vulnerable read path never runs.","status":"published","published":"2026-10-26T13:30:24.621Z","modified":"2026-10-26T13:56:07.167679161Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-835","CWE-770"],"updated_at":"2026-11-02T15:46:33.047032Z"},{"id":"UBUNTU-CVE-2026-115269","description":"Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 request body reader of mtrudel bandit allows an unauthenticated remote attacker to hold stream processes open indefinitely via WINDOW_UPDATE or empty SETTINGS frames sent while a Plug reads the request body. Bandit.HTTP2.Stream.do_read_data/4 in lib/bandit/http2/stream.ex waits for each frame with a fresh read_timeout. A stream WINDOW_UPDATE, or the zero-delta window update that every empty SETTINGS frame delivers to all streams, ends the wait without delivering any body data, and the loop starts a new full countdown. A client that sends one of these 9-byte frames before each countdown expires keeps read_body blocked, together with the stream process and whatever the application holds while reading, for as long as it likes. This issue affects bandit: from 1.4.0 before 1.14.0.","status":"published","published":"2026-10-26T14:16:00Z","modified":"2026-10-28T20:18:18.223965961Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"},{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T16:55:59.591851Z"}]}}