{"id":"CVE-2026-73253","title":"Mongoose is an embedded web server and network library","summary":"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…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","cwe":["CWE-295"],"vendor":"cesanta","product":"mongoose","affected":["mongoose < 7.22"],"patched":["mongoose 7.22"],"published":"2026-08-20","updated":"2026-09-29","sourceUpdated":"2026-09-29T15:38:46.537","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-73253","references":[{"url":"https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71","label":"security-advisories@github.com"},{"url":"https://github.com/cesanta/mongoose/pull/3611","label":"security-advisories@github.com"},{"url":"https://github.com/cesanta/mongoose/releases/tag/7.22","label":"security-advisories@github.com"},{"url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp","label":"security-advisories@github.com"},{"url":"https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73253.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-73253"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-73253"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.00344,"epssPercentile":0.27751,"ingestedAt":"2026-09-09T21:22:45.545Z","slug":"CVE-2026-73253","body":"## Overview\n\nMongoose 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.\n\n## Affected\n\n- `mongoose < 7.22`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `mongoose 7.22`\n\n## Vendor advisories\n\n- **Red Hat VEX** · updated 2026-09-25 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-73253.json)","depth":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":211329,"id":"CVE-2026-73253","ts":1790408708118,"field":"cvss","old":null,"new":"9.1"},{"seq":211328,"id":"CVE-2026-73253","ts":1790408708118,"field":"severity","old":"none","new":"critical"}]}