{"id":"UBUNTU-CVE-2026-73253","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.","modified":"2026-10-17T13:01:02.349475879Z","published":"2026-08-20T18:16:00Z","upstream":["CVE-2026-73253"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-73253"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-73253"}],"affected":[{"package":{"name":"mongoose","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/mongoose?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.21+ds-1","7.21+ds-2","7.22+ds-1","7.23+ds-1"],"ecosystem_specific":{"binaries":[{"binary_version":"7.23+ds-1","binary_name":"mongoose-webserver-source"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-73253.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}