CVE-2026-73253

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.

References

• https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71
• https://github.com/cesanta/mongoose/pull/3611
• https://github.com/cesanta/mongoose/releases/tag/7.22
• https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp
• https://github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vp