CVE-2026-42012

A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.

This vulnerability is rated as Moderate severity because exploitation requires an active man-in-the-middle position or tricking a client into connecting to a rogue endpoint, along with obtaining a validly signed certificate containing specialized SAN fields. While GnuTLS is widely deployed across Red Hat products as a core cryptographic library, the impact is limited to hostname verification spoofing under specific certificate configurations. The issue does not permit remote code execution or direct compromise of the underlying system.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.