{"id":"EEF-CVE-2026-115269","summary":"HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit","details":"## 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.","aliases":["CVE-2026-115269","GHSA-p2qv-vx88-385x"],"modified":"2026-10-26T13:56:07.167679161Z","published":"2026-10-26T13:30:24.621Z","database_specific":{"capec_ids":["CAPEC-469"],"cpe_ids":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-835","CWE-770"]},"references":[{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-p2qv-vx88-385x"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-115269.html"},{"type":"WEB","url":"https://github.com/mtrudel/bandit/commit/fff06efe3be962b484bd4d3eb339372fda5a231f"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a"},{"type":"PACKAGE","url":"https://hex.pm/packages/bandit"}],"affected":[{"package":{"name":"bandit","ecosystem":"Hex","purl":"pkg:hex/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"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-115269.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/mtrudel/bandit","events":[{"introduced":"fff06efe3be962b484bd4d3eb339372fda5a231f"},{"fixed":"220b9dfd27f9a21305be2afc75cbe585ddc24e7a"}]}],"versions":["1.13.1","1.13.0","1.12.5","1.12.4","1.12.3","1.12.1","1.12.0","1.11.1","1.11.0","1.10.4","1.10.3","1.10.2","1.10.1","1.10.0","1.9.0","1.8.0","1.7.0","1.6.11","1.6.10","1.6.9","1.6.8","1.6.7","1.6.6","1.6.5","1.6.4","1.6.3","1.6.2","1.6.1","1.6.0","1.5.7","1.5.6","1.5.5","1.5.4","1.5.3","1.5.2","1.5.1","1.5.0","1.4.2","1.4.1","1.4.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-115269.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}],"credits":[{"name":"Peter Ullrich","type":"ANALYST"},{"name":"Daniel Coles","type":"REPORTER"},{"name":"Mat Trudel","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"ANALYST"}]}