Improper Certificate Validation in GnuTLS - CVE-2026-42012

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Main Vulnerability Database Vulnerabilities #VU128574

Improper Certificate Validation in GnuTLS - CVE-2026-42012

Published: April 30, 2026


Vulnerability identifier: #VU128574
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-42012
CWE-ID: CWE-295
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to misuse certificates beyond their intended purpose.

The vulnerability exists due to improper certificate validation in certificate hostname verification when processing certificates containing URI or SRV Subject Alternative Names. A remote attacker can present a specially crafted certificate to misuse certificates beyond their intended purpose.

Certificates with URI or SRV Subject Alternative Names may incorrectly fall back to checking DNS hostnames against the Common Name.


Affected software

GnuTLS
Debian Linux
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Enterprise Micro
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Basesystem Module
openSUSE Leap
Ubuntu
openEuler
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
gnutls (Red Hat package)
gnutls28 (Ubuntu package)
gnutls-help
gnutls
gnutls-debuginfo
gnutls-utils
gnutls-devel
gnutls-debugsource
gnutls-dane
gnutls-c++
libgnutlsxx28-debuginfo
libgnutlsxx-devel
gnutls-guile-debuginfo
libgnutls30
libgnutls30-hmac
libgnutls30-64bit-debuginfo
libgnutls30-debuginfo
gnutls-guile
libgnutls30-hmac-64bit
libgnutls-devel-64bit
libgnutlsxx28
libgnutls30-32bit-debuginfo
libgnutls30-64bit
libgnutls30-hmac-32bit
libgnutls-devel
libgnutls-devel-32bit
libgnutls30-32bit
gnutls28 (Debian package)
gnutls-doc
libgnutlsxx30-debuginfo
libgnutlsxx30
libtasn1 (Red Hat package)

How to mitigate CVE-2026-42012

Install security update from vendor's website.

GnuTLS - update to 3.8.13
gnutls (Red Hat package) - addressed in versions 3.3.29-9.el7_9.2, 3.6.14-10.el8_4.1, 3.6.16-5.el8_6.5, 3.7.6-21.el9_2.7, 3.8.9-9.el10_0.19
gnutls28 (Ubuntu package) - addressed in versions 3.4.10-4ubuntu1.9+esm4, 3.5.18-1ubuntu1.6+esm4, 3.6.13-2ubuntu1.12+esm3, 3.7.3-4ubuntu1.9, 3.8.3-1.1ubuntu3.6, 3.8.9-3ubuntu2.2, 3.8.12-2ubuntu1.1
gnutls-help - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls-debuginfo - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls-utils - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls-devel - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls-debugsource - addressed in versions 3.6.14-24, 3.7.2-25, 3.8.2-16
gnutls-utils - addressed in versions 3.6.16-8.0.2, 3.8.2-9
gnutls-devel - addressed in versions 3.6.16-8.0.2, 3.8.2-9
gnutls-dane - addressed in versions 3.6.16-8.0.2, 3.8.2-9
gnutls-c++ - addressed in versions 3.6.16-8.0.2, 3.8.2-9
gnutls - addressed in versions 3.6.16-8.0.2, 3.8.2-9
libgnutlsxx28-debuginfo - update to 3.7.3-150400.4.59.1
libgnutlsxx-devel - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
gnutls-guile-debuginfo - update to 3.7.3-150400.4.59.1
gnutls - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2, 3.8.3-150600.4.20.1
gnutls-debuginfo - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2, 3.8.3-150600.4.20.1
libgnutls30 - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2, 3.8.3-150600.4.20.1
libgnutls30-hmac - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2
libgnutls30-64bit-debuginfo - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
gnutls-debugsource - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2, 3.8.3-150600.4.20.1
libgnutls30-debuginfo - addressed in versions 3.7.3-150400.4.59.1, 3.7.3-150400.24.2, 3.8.3-150600.4.20.1
gnutls-guile - update to 3.7.3-150400.4.59.1
libgnutls30-hmac-64bit - update to 3.7.3-150400.4.59.1
libgnutls-devel-64bit - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
libgnutlsxx28 - update to 3.7.3-150400.4.59.1
libgnutls30-32bit-debuginfo - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
libgnutls30-64bit - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
libgnutls30-hmac-32bit - update to 3.7.3-150400.4.59.1
libgnutls-devel - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
libgnutls-devel-32bit - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
libgnutls30-32bit - addressed in versions 3.7.3-150400.4.59.1, 3.8.3-150600.4.20.1
gnutls28 (Debian package) - addressed in versions 3.7.9-2+deb12u7, 3.8.9-3+deb13u4
gnutls-doc - update to 3.8.2-9
gnutls-dane - update to 3.8.2-16
libgnutlsxx30-debuginfo - update to 3.8.3-150600.4.20.1
libgnutlsxx30 - update to 3.8.3-150600.4.20.1
libtasn1 (Red Hat package) - addressed in versions 4.13-3.el8_4.1, 4.13-3.el8_6.2

External References

Related Security Bulletins