Is CVE-2026-42012 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-42012 being exploited in the wild.

How severe is CVE-2026-42012?

High severity, with a CVSS score of 7.1, published 26 May 2026.

Is there a fix for CVE-2026-42012?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-42012 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-42012?

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.

CVE-2026-42012: GnuTLS certificate validation bypass in URI and SRV SAN handling

CVE-2026-42012 · Severity: high · CVSS 7.1 · Published 2026-05-26

GnuTLS is a widely used security library that helps applications establish secure, encrypted connections. A flaw in how it validates digital certificates could allow an attacker to impersonate a legitimate website or service. This could lead to users unknowingly connecting to a malicious server, potentially resulting in the theft of sensitive login credentials or private data.

Quick answers

Is CVE-2026-42012 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-42012 being exploited in the wild.
How severe is CVE-2026-42012?: High severity, with a CVSS score of 7.1, published 26 May 2026.
Which products and versions are affected?: GnuTLS gnutls.
Is there a fix for CVE-2026-42012?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-42012 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-42012?: 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

A vulnerability exists in GnuTLS (CWE-295) due to improper handling of Subject Alternative Names (SANs). When a certificate contains Uniform Resource Identifier (URI) or Service (SRV) SANs, the validation logic incorrectly falls back to checking the DNS hostname against the Common Name (CN) field. This logic failure bypasses the standard requirement that SANs, if present, must be the sole source for identity verification. A remote attacker can exploit this by presenting a crafted certificate to a client application using GnuTLS, potentially allowing for service spoofing or man-in-the-middle (MitM) attacks. The fix involves suppressing the CN fallback mechanism when URI or SRV SANs are detected.

Affected products

GnuTLS gnutls

Timeline

2026-05-06: disclosed: Initial report in Red Hat Bugzilla
2026-05-26: advisory: NVD publication date

References

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