{"id":"CVE-2026-73253","aliases":["GHSA-jp6g-796f-39vp"],"url":"https://o3.security/vulnerability/CVE-2026-73253","summary":"Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching","details":"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.","published":"2026-08-20T17:41:02.495Z","modified":"2026-08-22T03:58:10.348375016Z","cvss":null,"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-2026-73253.json"},{"type":"ADVISORY","url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73253"},{"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":"2026-08-22T03:58:10.348375016Z"}}