GNUTLS Certificate Validation Bypass via URI/SRV SAN Fallback
CVE-2026-42012 Published on May 26, 2026

Gnutls: gnutls: certificate validation bypass due to improper handling of uri and srv sans
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.

Vendor Advisory Vendor Advisory Vendor Advisory Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-42012 is exploitable with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a high impact on integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
REQUIRED
Scope:
UNCHANGED
Confidentiality Impact:
LOW
Integrity Impact:
HIGH
Availability Impact:
NONE

Timeline

Reported to Red Hat.

Made public.

Weakness Type

Improper Certificate Validation

The software does not validate, or incorrectly validates, a certificate. When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The software might connect to a malicious host while believing it is a trusted host, or the software might be deceived into accepting spoofed data that appears to originate from a trusted host.


Products Associated with CVE-2026-42012

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2026-42012 are published in these products:

Canonical Ubuntu Linux
 
Red Hat Enterprise Linux (RHEL)
 
Red Hat Hummingbird
 
Red Hat Openshift
 
Red Hat Enterprise Linux Eus
 
Red Hat Rhui
 

Affected Versions

Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 10.0 Extended Update Support: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Update Infrastructure 5: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat Hardened Images: Red Hat OpenShift Container Platform 4:

Exploit Probability

EPSS
0.04%
Percentile
13.93%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.