Quick answers
- Is CVE-2026-73251 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-73251 being exploited in the wild.
- How severe is CVE-2026-73251?
- Informational severity, published 20 August 2026.
- Which products and versions are affected?
- Cesanta Mongoose prior to 7.23.
- Is there a fix for CVE-2026-73251?
- A patch was published on 2026-08-12: Fixed in version 7.23 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-73251 attacked?
- It is attacked over the network or from the adjacent network, in a software library.
- Am I affected by CVE-2026-73251?
- Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a TLS certificate verification bypass in the built-in TLS implementation. When mg_tls_init() loads a multi-certificate CA bundle, it stores the bundle in tls->ca_bundle_der but leaves tls->ca_der.len at zero. The mg_tls_recv_cert() function then uses tls_bundle_find() to match certificates by Common Name without calling mg_tls_verify_cert_signature(), allowing a forged self-signed certificate to pass hostname verification and CertificateVerify checks. The attack requires network position to intercept TLS connections but no authentication or user interaction. An attacker can perform man-in-the-middle attacks to intercept, eavesdrop on, and modify encrypted communications. The vulnerability is fixed in Mongoose 7.23.
Affected products
- Cesanta Mongoose prior to 7.23
Timeline
- 2026-08-20: disclosed
- 2026-08-12: patched: Fixed in version 7.23