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Vulnerability · Published May 26, 2026 · Assigned by redhat

CVE-2026-42013Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name

High 8.2

In plain English

A high-severity improper certificate validation in gnutls. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.2High
Exploit odds (30 days)0.4%top 63.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10gnutls3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-c++3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-c++3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-c++3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-dane3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-dane3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-dane3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-devel3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-devel3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-devel3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-fips3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:10gnutls-utils3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-utils3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-utils3.8.10-4.el9_8ALSA-2026:20612
Alpine:v3.20gnutls3.8.13-r0ALPINE-CVE-2026-42013
Alpine:v3.21gnutls3.8.13-r0ALPINE-CVE-2026-42013
Alpine:v3.22gnutls3.8.13-r0ALPINE-CVE-2026-42013
Alpine:v3.23gnutls3.8.13-r0ALPINE-CVE-2026-42013
Alpine:v3.24gnutls3.8.13-r0ALPINE-CVE-2026-42013
Debian:12gnutls283.7.9-2+deb12u7DEBIAN-CVE-2026-42013
Debian:13gnutls283.8.9-3+deb13u4DEBIAN-CVE-2026-42013
Debian:14gnutls283.8.13-1DEBIAN-CVE-2026-42013
Rocky Linux:10gnutls0:3.8.10-4.el10_2RLSA-2026:20613
Rocky Linux:8gnutls0:3.6.16-8.el8_10.6RLSA-2026:20611
Rocky Linux:9gnutls0:3.8.10-4.el9_8RLSA-2026:20612
Ubuntu:22.04:LTSgnutls283.7.3-4ubuntu1.9UBUNTU-CVE-2026-42013
Ubuntu:24.04:LTSgnutls283.8.3-1.1ubuntu3.6UBUNTU-CVE-2026-42013
Ubuntu:25.10gnutls283.8.9-3ubuntu2.2UBUNTU-CVE-2026-42013
Ubuntu:26.04:LTSgnutls283.8.12-2ubuntu1.1UBUNTU-CVE-2026-42013

Affected products (as reported)

VendorProductVersions
gnutls 0
Red Hat Red Hat Enterprise Linux 10 see references
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support see references
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service see references
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service see references
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9 see references
Red Hat Red Hat Enterprise Linux 9 see references
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support see references
Red Hat Red Hat OpenShift Container Platform 4.12 see references
Red Hat Red Hat OpenShift Container Platform 4.16 see references
Red Hat Red Hat OpenShift Container Platform 4.17 see references
Red Hat Red Hat OpenShift Container Platform 4.18 see references
Red Hat Red Hat OpenShift Container Platform 4.19 see references
Red Hat Red Hat OpenShift Container Platform 4.20 see references
Red Hat Red Hat OpenShift Container Platform 4.21 see references

Weakness: CWE-295 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

References