{"id":"CVE-2026-73253","state":"PUBLISHED","title":"Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching","description":"Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. This issue is fixed in version 7.22.","publishedAt":"2026-08-20T17:41:02.495Z","updatedAt":"2026-08-20T18:36:17.262Z","severity":{"score":9.1,"label":"Critical","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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-jp6g-796f-39vp","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-295"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/73xxx/CVE-2026-73253.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-73253","state":"PUBLISHED","datePublished":"2026-08-20T17:41:02.495Z","dateUpdated":"2026-08-20T18:36:17.262Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-11T17:18:01.598Z"},"containers":{"cna":{"title":"Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching","descriptions":[{"lang":"en","value":"Mongoose is an embedded web server and network library. Prior to version 7.22, an on-path network attacker with a wildcard certificate for a parent domain can impersonate deeper subdomains to a client using the built-in TLS stack. The mg_tls_verify_cert_san() and mg_tls_verify_cert_cn() functions in src/tls_builtin.c call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern such as *.example.com can match foo.bar.example.com. The resulting hostname verification bypass permits interception and modification of TLS traffic. 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-jp6g-796f-39vp","name":"https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp","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":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-295","lang":"en","description":"CWE-295: Improper Certificate Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-20T17:41:02.495Z"},"source":{"advisory":"GHSA-jp6g-796f-39vp","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-20T18:33:38.834878Z","id":"CVE-2026-73253","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-20T18:36:17.262Z"}}]}}}