CVE-2026-42013

Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name

State: Published
Severity: 8.2 High
Published: May 26, 2026
Updated: Oct 30, 2026
Reserved: Apr 23, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.2 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N	redhat

Weaknesses

CWE-295 Improper Certificate Validation

Affected Products

Product	Versions
gnutls	0Affected
Red Hat Enterprise Linux 10Red Hat	0:3.8.10-4.el10_2 and laterNot affected
Red Hat Enterprise Linux 10.0 Extended Update SupportRed Hat	0:3.8.9-9.el10_0.19 and laterNot affected
Red Hat Enterprise Linux 7 Extended Lifecycle SupportRed Hat	0:3.3.29-9.el7_9.2 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:3.6.16-8.el8_10.6 and laterNot affected
Red Hat Enterprise Linux 8Red Hat	0:3.6.16-8.el8_10.6 and laterNot affected
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportRed Hat	0:3.6.14-10.el8_4.1 and laterNot affected
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportRed Hat	0:4.13-3.el8_4.1 and laterNot affected
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnRed Hat	0:3.6.14-10.el8_4.1 and laterNot affected
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnRed Hat	0:4.13-3.el8_4.1 and laterNot affected
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportRed Hat	0:3.6.16-5.el8_6.5 and laterNot affected
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportRed Hat	0:4.13-3.el8_6.2 and laterNot affected
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnRed Hat	0:3.6.16-5.el8_6.5 and laterNot affected
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-OnRed Hat	0:4.13-3.el8_6.2 and laterNot affected
Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceRed Hat	0:3.6.16-7.el8_8.4 and laterNot affected
Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceRed Hat	0:4.13-4.el8_8.1 and laterNot affected
Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsRed Hat	0:3.6.16-7.el8_8.4 and laterNot affected
Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsRed Hat	0:4.13-4.el8_8.1 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:3.8.10-4.el9_8 and laterNot affected
Red Hat Enterprise Linux 9Red Hat	0:3.8.10-4.el9_8 and laterNot affected
Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsRed Hat	0:3.7.6-21.el9_2.7 and laterNot affected
Red Hat Enterprise Linux 9.4 Update Services for SAP SolutionsRed Hat	0:3.8.3-4.el9_4.6 and laterNot affected
Red Hat Enterprise Linux 9.6 Extended Update SupportRed Hat	0:3.8.3-6.el9_6.4 and laterNot affected
Red Hat OpenShift Container Platform 4.12Red Hat	412.86.202608241157-0 and laterNot affected
Red Hat OpenShift Container Platform 4.16Red Hat	416.94.202608150307-0 and laterNot affected
Red Hat OpenShift Container Platform 4.17Red Hat	417.94.202608250221-0 and laterNot affected
Red Hat OpenShift Container Platform 4.18Red Hat	418.94.202608142238-0 and laterNot affected
Red Hat OpenShift Container Platform 4.19Red Hat	4.19.9.6.202607151909-0 and laterNot affected
Red Hat OpenShift Container Platform 4.20Red Hat	4.20.9.6.202610242033-0 and laterNot affected
Red Hat OpenShift Container Platform 4.21Red Hat	4.21.9.6.202610241345-0 and laterNot affected
Red Hat OpenShift Container Platform 4.22Red Hat	4.22.9.8.202610241758-0 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.17Red Hat	1791371080 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.17Red Hat	1791371069 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.17Red Hat	1791788287 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.17Red Hat	1791970484 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.18Red Hat	1791459707 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.18Red Hat	1791459711 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.18Red Hat	1791459759 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.18Red Hat	1789029076 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.18Red Hat	1791966259 and laterNot affected
Cert Manager support for Red Hat OpenShift release 1.20Red Hat	1790598593 and laterNot affected
Red Hat Discovery 2Red Hat	1782159791 and laterNot affected
Red Hat Discovery 2Red Hat	1782166952 and laterNot affected
Red Hat Hardened ImagesRed Hat	3.8.13-1.hum1 and laterNot affected
Red Hat OpenShift AI 3.4Red Hat	1790703542 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1781525684 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1781525671 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1781525693 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1781525739 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1787241211 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1787135742 and laterNot affected
Red Hat Update Infrastructure 5Red Hat	1787241260 and laterNot affected
Red Hat Enterprise Linux 6Red Hat
Red Hat OpenShift Container Platform 4Red Hat
Red Hat OpenShift Container Platform 5Red Hat

References

RHSA-2026:13274vendor-advisory
RHSA-2026:20611vendor-advisory
RHSA-2026:20612vendor-advisory
RHSA-2026:20613vendor-advisory
RHSA-2026:26319vendor-advisory
RHSA-2026:26409vendor-advisory
RHSA-2026:29197vendor-advisory
RHSA-2026:30004vendor-advisory
RHSA-2026:30849vendor-advisory
RHSA-2026:30850vendor-advisory
RHSA-2026:32962vendor-advisory
RHSA-2026:33125vendor-advisory
RHSA-2026:40762vendor-advisory
RHSA-2026:41921vendor-advisory
RHSA-2026:43575vendor-advisory
RHSA-2026:56853vendor-advisory
RHSA-2026:57483vendor-advisory
RHSA-2026:58981vendor-advisory
RHSA-2026:59831vendor-advisory
RHSA-2026:60019vendor-advisory
RHSA-2026:72502vendor-advisory
RHSA-2026:74674vendor-advisory
RHSA-2026:82304vendor-advisory
RHSA-2026:82322vendor-advisory
RHSA-2026:82347vendor-advisory
RHSA-2026:82354vendor-advisory
RHSA-2026:82372vendor-advisory
RHSA-2026:82857vendor-advisory
RHSA-2026:82888vendor-advisory
RHSA-2026:89197vendor-advisory
RHSA-2026:89232vendor-advisory
RHSA-2026:89333vendor-advisory
https://access.redhat.com/security/cve/CVE-2026-42013vdb-entry
RHBZ#2467448issue-tracking
https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-8

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