{"id":"CVE-2026-73256","state":"PUBLISHED","title":"Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE","description":"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.","publishedAt":"2026-08-20T17:37:54.505Z","updatedAt":"2026-08-21T21:46:47.832Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["cesanta mongoose"],"affected":[{"vendor":"cesanta","product":"mongoose","versions":[{"version":"< 7.22","status":"affected"}]}],"references":["https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3","https://github.com/cesanta/mongoose/pull/3611","https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71","https://github.com/cesanta/mongoose/releases/tag/7.22"],"weaknesses":["CWE-444"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/73xxx/CVE-2026-73256.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-73256","state":"PUBLISHED","datePublished":"2026-08-20T17:37:54.505Z","dateUpdated":"2026-08-21T21:46:47.832Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-11T17:18:01.598Z"},"containers":{"cna":{"title":"Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"cesanta","product":"mongoose","versions":[{"version":"< 7.22","status":"affected"}]}],"references":[{"url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3","name":"https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/cesanta/mongoose/pull/3611","name":"https://github.com/cesanta/mongoose/pull/3611","tags":["x_refsource_MISC"]},{"url":"https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71","name":"https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71","tags":["x_refsource_MISC"]},{"url":"https://github.com/cesanta/mongoose/releases/tag/7.22","name":"https://github.com/cesanta/mongoose/releases/tag/7.22","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-444","lang":"en","description":"CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-20T17:37:54.505Z"},"source":{"advisory":"GHSA-mgp5-rjrv-h5j3","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-21T21:10:40.015064Z","id":"CVE-2026-73256","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-21T21:46:47.832Z"}}]}}}