{"id":"CVE-2026-73257","aliases":["GHSA-5wfq-r6mr-wqp6"],"url":"https://o3.security/vulnerability/CVE-2026-73257","summary":"Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling","details":"Mongoose is an embedded web server and network library. Priro to version 7.22, a remote unauthenticated attacker can send an HTTP request containing both Content-Length and Transfer-Encoding: chunked. The cl_count and te_count checks in the mg_http_parse() and http_cb() paths in src/http.c accept both headers and prioritize chunked encoding, while a Content-Length-preferring reverse proxy can use a different request boundary. This CL.TE desynchronization can inject requests that access or modify resources in another user context. This issue is fixed in version 7.22.","published":"2026-08-20T17:30:58.424Z","modified":"2026-08-22T03:49:48.233515431Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":{"url":"https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71","label":"cesanta/mongoose@a9df523"},"references":[{"type":"WEB","url":"https://github.com/cesanta/mongoose/releases/tag/7.22"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73257.json"},{"type":"ADVISORY","url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-5wfq-r6mr-wqp6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73257"},{"type":"FIX","url":"https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71"},{"type":"FIX","url":"https://github.com/cesanta/mongoose/pull/3611"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-22T03:49:48.233515431Z"}}