{"id":"EEF-CVE-2026-39803","summary":"HTTP/1 chunked body reader ignores length cap in bandit","details":"## Summary\n\nAllocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion.\n\nThe chunked clause of 'Elixir.Bandit.HTTP1.Socket':read_data/2 in lib/bandit/http1/socket.ex ignores the caller-supplied :length option when reading HTTP/1 chunked request bodies. Instead of capping the accumulated body at the configured limit (e.g. Plug.Parsers' default 8 MB), do_read_chunked_data!/5 buffers every received chunk into an iolist unconditionally and materializes the entire body as a single binary. The function always returns {:ok, body, ...}, so callers cannot interpose a 413 response.\n\nBecause Plug.Parsers runs before routing and authentication in the standard Phoenix endpoint, an unauthenticated attacker needs no valid route or credentials. Sending a single Transfer-Encoding: chunked POST request with an arbitrarily large body to any path causes the BEAM process to exhaust available memory and be terminated by the OS OOM killer.\n\nThe content-length path in the same function correctly enforces the limit and is not affected.\n\nThis issue affects bandit: from 1.4.0 before 1.11.1.","aliases":["CVE-2026-39803","GHSA-9q9q-324x-93r2"],"modified":"2026-05-13T18:27:30.095Z","published":"2026-05-13T13:36:09.648Z","database_specific":{"capec_ids":["CAPEC-130"],"cpe_ids":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-770"]},"references":[{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-39803.html"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab"},{"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":"1.11.1"}]}],"versions":["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","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.6.10","1.6.11","1.7.0","1.8.0","1.9.0","1.10.0","1.10.1","1.10.2","1.10.3","1.10.4","1.11.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-39803.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/mtrudel/bandit","events":[{"introduced":"903e209a521bc216b9f9065c01ae9a0cac2d5a10"},{"fixed":"ae3520dfdbfab115c638f8c7f6f6b805db34e1ab"}]}],"versions":["1.10.0","1.10.1","1.10.2","1.10.3","1.10.4","1.11.0","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-2026-39803.json"}}],"schema_version":"1.7.5","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":"FINDER"},{"name":"Mat Trudel","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen","type":"ANALYST"}]}