by Kastro
Paper/Archive/CVE-2026-73253

CVE-2026-73253

cesanta mongoose — Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching

EPSS 0.3%public exploitCVSS 9.1
critical.is priorityof 100
43
CVSS 9.1 (CNA, NVD agree)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 27.9.279 × 205.6Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
mongoose< 7.22–CNA

Scores by source

GitHub_M (CNA)9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADPSSVCExploitation: poc · Automatable: no · Technical impact: total

References

exploitgithub.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-39vprefgithub.com/cesanta/mongoose/pull/3611refgithub.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71refgithub.com/cesanta/mongoose/releases/tag/7.22