CVE-2026-73253
CriticalCVSS 9.1Summary
A vulnerability in Mongoose before version 7.22 allows an on-path network attacker with a wildcard certificate for a parent domain to 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 call mg_match(), whose wildcard can cross DNS label boundaries, so a pattern like *.example.com can match foo.bar.example.com.
Risk Assessment
The risk includes interception and modification of TLS traffic, potentially leading to disclosure of sensitive data.
Recommendation
Upgrade Mongoose to version 7.22 or later, which includes the fix.
Original NVD description (English source)
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.