{"id":"CVE-2026-73256","aliases":["GHSA-mgp5-rjrv-h5j3"],"url":"https://o3.security/vulnerability/CVE-2026-73256","summary":"Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE","details":"Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.","published":"2026-08-20T17:37:54.505Z","modified":"2026-08-22T03:58:10.479077213Z","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-2026-73256.json"},{"type":"ADVISORY","url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73256"},{"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":"2026-08-22T03:58:10.479077213Z"}}