CVE-2026-73251
Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.19%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls_builtin.c, the mg_tls_init() function stores the bundle in tls->ca_bundle_der while tls->ca_der.len remains zero, and mg_tls_recv_cert() uses tls_bundle_find() to accept a Common Name match without calling mg_tls_verify_cert_signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.
- CVSS 4.0
- 9.3 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/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/M
- EPSS
- 0.19% probability · 9th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-295
- Source
- security-advisories@github.com
References
- https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483
- https://github.com/cesanta/mongoose/releases/tag/7.23
- https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
- https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
- https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
- https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.