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.
Affected products
cesanta: mongoose
References5
- github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-… ExploitVendor Advisory
- github.com/cesanta/mongoose/security/advisories/GHSA-jp6g-796f-… ExploitVendor Advisory
- github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9c… Patch
- github.com/cesanta/mongoose/pull/3611 Issue TrackingPatch
- github.com/cesanta/mongoose/releases/tag/7.22 Release Notes
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS 4.0
-
9.1
CRITICAL
Score source: CNA
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 28 · as of 10 November 2026
- CWE
- CWE-295
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.