{"id":"CVE-2026-39803","aliases":["EEF-CVE-2026-39803","GHSA-9q9q-324x-93r2"],"url":"https://o3.security/vulnerability/CVE-2026-39803","summary":"HTTP/1 chunked body reader ignores length cap in bandit","details":"Allocation 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.","published":"2026-05-13T13:36:09.648Z","modified":"2026-08-12T03:51:44.839581439Z","cvss":null,"epss":{"score":0.00642,"percentile":0.47674,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"bandit","fixedVersion":"1.11.1"}],"fix":{"url":"https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab","label":"mtrudel/bandit@ae3520d"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-39803.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-39803"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39803.json"},{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39803"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab"},{"type":"PACKAGE","url":"https://github.com/mtrudel/bandit"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:44.839581439Z"}}