CVE-2026-73251

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

9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 8% of CVEs (scores of 2026-10-25)

CWE

CWE-295

Published

2026-08-20

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

Affected

• cesanta:mongoose

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

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