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Fencer Vulns
high 8.2

CVE-2026-42013 json

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

published 2026-05-26 5 mo ago modified 2026-11-05 3 d ago also EUVD-2026-32011

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

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.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 0:3.8.10-4.el10_2
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:3.8.9-9.el10_0.19
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:3.3.29-9.el7_9.2
  • Red Hat Red Hat Enterprise Linux 8 0:3.6.16-8.el8_10.6
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:3.6.16-5.el8_6.5, 0:4.13-3.el8_6.2
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On 0:3.6.16-5.el8_6.5, 0:4.13-3.el8_6.2
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:3.6.16-7.el8_8.4, 0:4.13-4.el8_8.1
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:3.6.16-7.el8_8.4, 0:4.13-4.el8_8.1
  • Red Hat Red Hat Enterprise Linux 9 0:3.8.10-4.el9_8
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:3.7.6-21.el9_2.7
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 0:3.8.3-4.el9_4.6
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:3.8.3-6.el9_6.4
  • Red Hat Red Hat OpenShift Container Platform 4.12 412.86.202608241157-0
  • Red Hat Red Hat OpenShift Container Platform 4.16 416.94.202608150307-0
  • Red Hat Red Hat OpenShift Container Platform 4.17 417.94.202608250221-0
  • Red Hat Red Hat OpenShift Container Platform 4.18 418.94.202608142238-0
  • Red Hat Red Hat OpenShift Container Platform 4.19 4.19.9.6.202607151909-0
  • Red Hat Red Hat OpenShift Container Platform 4.20 4.20.9.6.202610242033-0
  • Red Hat Red Hat OpenShift Container Platform 4.21 4.21.9.6.202610241345-0
  • Red Hat Red Hat OpenShift Container Platform 4.22 4.22.9.8.202610241758-0
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.17 1791371069, 1791371080, 1791788287, 1791970484
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.18 1789029076, 1791459707, 1791459711, 1791459759, 1791966259
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 1790598593
  • Red Hat Red Hat Discovery 2 1782159791, 1782166952
  • Red Hat Red Hat Hardened Images 3.8.13-1.hum1
  • Red Hat Red Hat OpenShift AI 3.4 1790703542
  • Red Hat Red Hat Update Infrastructure 5 1781525671, 1781525684, 1781525693, 1781525739, 1787135742, 1787241211, 1787241260
  • gnutls28 Debian 12 3.7.9-2+deb12u7
  • gnutls28 Debian 13 3.8.9-3+deb13u4
  • gnutls28 Debian 14 3.8.13-1

debian advisories DEBIAN-CVE-2026-42013

  • gnutls28 Ubuntu 22.04 LTS 3.7.3-4ubuntu1.9
  • gnutls28 Ubuntu 24.04 LTS 3.8.3-1.1ubuntu3.6
  • gnutls28 Ubuntu 25.10 3.8.9-3ubuntu2.2
  • gnutls28 Ubuntu 26.04 LTS 3.8.12-2ubuntu1.1
  • gnutls28 Ubuntu Pro 16.04 LTS 3.4.10-4ubuntu1.9+esm4
  • gnutls28 Ubuntu Pro 18.04 LTS 3.5.18-1ubuntu1.6+esm4
  • gnutls28 Ubuntu Pro 20.04 LTS 3.6.13-2ubuntu1.12+esm3
  • gnutls28 Ubuntu Pro FIPS-updates 22.04 LTS 3.7.3-4ubuntu1.9+Fips1

ubuntu advisories UBUNTU-CVE-2026-42013

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • gnutls RHEL 9 3.8.10-4.el9_8
  • gnutls-c++ RHEL 9 3.8.10-4.el9_8
  • gnutls-dane RHEL 9 3.8.10-4.el9_8
  • gnutls-utils RHEL 9 3.8.10-4.el9_8
  • gnutls RHEL 10.2 3.8.10-4.el10_2
  • gnutls-c++ RHEL 10.2 3.8.10-4.el10_2
  • gnutls-dane RHEL 10.2 3.8.10-4.el10_2
  • gnutls-fips RHEL 10.2 3.8.10-4.el10_2

red hat advisories RHSA-2026:43575RHSA-2026:41921RHSA-2026:33125RHSA-2026:32962RHSA-2026:30850RHSA-2026:30849

  • gnutls SLE Micro 5.3 3.7.3-150400.24.2
  • gnutls SLES LTSS Extended Security 12 SP5 3.3.27-3.21.1
  • gnutls SLES LTSS Extended Security 12 SP5 3.4.17-8.26.1

suse advisories SUSE-SU-2026:2924-1SUSE-SU-2026:2923-1SUSE-SU-2026:2822-1

  • gnutls openSUSE Tumbleweed 3.8.13-1.1

opensuse advisories openSUSE-SU-2026:10691-1

  • gnutls AlmaLinux 8 3.6.16-8.el8_10.6
  • gnutls-c++ AlmaLinux 8 3.6.16-8.el8_10.6
  • gnutls-dane AlmaLinux 8 3.6.16-8.el8_10.6
  • gnutls-utils AlmaLinux 8 3.6.16-8.el8_10.6
  • gnutls AlmaLinux 9 3.8.10-4.el9_8
  • gnutls-c++ AlmaLinux 9 3.8.10-4.el9_8
  • gnutls-dane AlmaLinux 9 3.8.10-4.el9_8
  • gnutls-utils AlmaLinux 9 3.8.10-4.el9_8

almalinux advisories ALSA-2026:20611ALSA-2026:20612ALSA-2026:20613

  • gnutls Rocky Linux 10 3.8.10-4.el10_2
  • gnutls Rocky Linux 9 3.8.10-4.el9_8
  • gnutls Rocky Linux 8 3.6.16-8.el8_10.6

rocky linux advisories RLSA-2026:20613RLSA-2026:20612RLSA-2026:20611

  • gnutls Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 3.8.13-r0

alpine advisories ALPINE-CVE-2026-42013

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • gnutls Azure Linux 3.0 3.8.13-1

azure linux advisories AZL-89178

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-42013 updated cvss 8.2

gnutls: gnutls: Certificate validation bypass due to oversized Subject Alternative Name

  • Red Hat Enterprise Linux 6 gnutls, gnutls-guile, gnutls-utils
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.17 cert-manager/cert-manager-operator-rhel9 1791788287, cert-manager/jetstack-cert-manager-rhel9 1791371069, cert-manager/cert-manager-operator-bundle 1791970484, cert-manager/jetstack-cert-manager-acmesolver-rhel9 1791371080
    fixed: vendor fix RHSA-2026:82888
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.18 cert-manager/cert-manager-operator-rhel9 1789029076, cert-manager/jetstack-cert-manager-rhel9 1791459711, cert-manager/cert-manager-istio-csr-rhel9 1791459759, cert-manager/cert-manager-operator-bundle 1791966259, cert-manager/jetstack-cert-manager-acmesolver-rhel9 1791459707
    fixed: vendor fix RHSA-2026:82354
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20 cert-manager/cert-manager-trust-manager-rhel9 1790598593
    fixed: vendor fix RHSA-2026:72502
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1782166952, discovery/discovery-server-rhel9 1782159791
    fixed: vendor fix RHSA-2026:29197
  • Red Hat Enterprise Linux AppStream (v. 8) gnutls-c++ 3.6.16-8.el8_10.6, gnutls-dane 3.6.16-8.el8_10.6, gnutls-utils 3.6.16-8.el8_10.6
    fixed: vendor fix RHSA-2026:20611
  • Red Hat Enterprise Linux AppStream (v. 9) gnutls-c++ 3.8.10-4.el9_8, gnutls-dane 3.8.10-4.el9_8, gnutls-utils 3.8.10-4.el9_8
    fixed: vendor fix RHSA-2026:20612
show 32 more
  • Red Hat Enterprise Linux AppStream (v. 10) gnutls-c++ 3.8.10-4.el10_2, gnutls-dane 3.8.10-4.el10_2, gnutls-fips 3.8.10-4.el10_2, gnutls-utils 3.8.10-4.el10_2
    fixed: vendor fix RHSA-2026:20613
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) gnutls-c++ 3.6.14-10.el8_4.1, gnutls-dane 3.6.14-10.el8_4.1, libtasn1-tools 4.13-3.el8_4.1, gnutls-utils 3.6.14-10.el8_4.1
    fixed: vendor fix RHSA-2026:33125
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) gnutls-c++ 3.6.16-5.el8_6.5, gnutls-dane 3.6.16-5.el8_6.5, gnutls-utils 3.6.16-5.el8_6.5, libtasn1-tools 4.13-3.el8_6.2
    fixed: vendor fix RHSA-2026:30849
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) gnutls-c++ 3.6.16-7.el8_8.4, gnutls-dane 3.6.16-7.el8_8.4, gnutls-utils 3.6.16-7.el8_8.4, libtasn1-tools 4.13-4.el8_8.1
    fixed: vendor fix RHSA-2026:30850
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) gnutls-c++ 3.7.6-21.el9_2.7, gnutls-dane 3.7.6-21.el9_2.7, gnutls-utils 3.7.6-21.el9_2.7
    fixed: vendor fix RHSA-2026:41921
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) gnutls-c++ 3.8.3-4.el9_4.6, gnutls-dane 3.8.3-4.el9_4.6, gnutls-utils 3.8.3-4.el9_4.6
    fixed: vendor fix RHSA-2026:32962
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) gnutls-c++ 3.8.9-9.el10_0.19, gnutls-dane 3.8.9-9.el10_0.19, gnutls-fips 3.8.9-9.el10_0.19, gnutls-utils 3.8.9-9.el10_0.19
    fixed: vendor fix RHSA-2026:26409
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) gnutls-c++ 3.8.3-6.el9_6.4, gnutls-dane 3.8.3-6.el9_6.4, gnutls-utils 3.8.3-6.el9_6.4
    fixed: vendor fix RHSA-2026:30004
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) gnutls-c++ 3.6.14-10.el8_4.1, gnutls-dane 3.6.14-10.el8_4.1, libtasn1-tools 4.13-3.el8_4.1, gnutls-utils 3.6.14-10.el8_4.1
    fixed: vendor fix RHSA-2026:33125
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) gnutls-c++ 3.6.16-5.el8_6.5, gnutls-dane 3.6.16-5.el8_6.5, gnutls-utils 3.6.16-5.el8_6.5, libtasn1-tools 4.13-3.el8_6.2
    fixed: vendor fix RHSA-2026:30849
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) gnutls-c++ 3.6.16-7.el8_8.4, gnutls-dane 3.6.16-7.el8_8.4, gnutls-utils 3.6.16-7.el8_8.4, libtasn1-tools 4.13-4.el8_8.1
    fixed: vendor fix RHSA-2026:30850
  • Red Hat Enterprise Linux BaseOS (v. 8) gnutls 3.6.16-8.el8_10.6
    fixed: vendor fix RHSA-2026:20611
  • Red Hat Enterprise Linux BaseOS (v. 9) gnutls 3.8.10-4.el9_8
    fixed: vendor fix RHSA-2026:20612
  • Red Hat Enterprise Linux BaseOS (v. 10) gnutls 3.8.10-4.el10_2
    fixed: vendor fix RHSA-2026:20613
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) libtasn1 4.13-3.el8_4.1, gnutls 3.6.14-10.el8_4.1
    fixed: vendor fix RHSA-2026:33125
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) gnutls 3.6.16-5.el8_6.5, libtasn1 4.13-3.el8_6.2
    fixed: vendor fix RHSA-2026:30849
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) gnutls 3.6.16-7.el8_8.4, libtasn1 4.13-4.el8_8.1
    fixed: vendor fix RHSA-2026:30850
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) gnutls 3.7.6-21.el9_2.7
    fixed: vendor fix RHSA-2026:41921
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) gnutls 3.8.3-4.el9_4.6
    fixed: vendor fix RHSA-2026:32962
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) gnutls 3.8.9-9.el10_0.19
    fixed: vendor fix RHSA-2026:26409
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) gnutls 3.8.3-6.el9_6.4
    fixed: vendor fix RHSA-2026:30004
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) libtasn1 4.13-3.el8_4.1, gnutls 3.6.14-10.el8_4.1
    fixed: vendor fix RHSA-2026:33125
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) gnutls 3.6.16-5.el8_6.5, libtasn1 4.13-3.el8_6.2
    fixed: vendor fix RHSA-2026:30849
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) gnutls 3.6.16-7.el8_8.4, libtasn1 4.13-4.el8_8.1
    fixed: vendor fix RHSA-2026:30850
  • Red Hat Enterprise Linux Server (v. 7 ELS) gnutls 3.3.29-9.el7_9.2, gnutls-c++ 3.3.29-9.el7_9.2, gnutls-dane 3.3.29-9.el7_9.2, gnutls-utils 3.3.29-9.el7_9.2
    fixed: vendor fix RHSA-2026:43575
  • Red Hat Hardened Images gnutls 3.8.13-1.hum1, gnutls-c++ 3.8.13-1.hum1, gnutls-dane 3.8.13-1.hum1, gnutls-fips 3.8.13-1.hum1, gnutls-utils 3.8.13-1.hum1, mingw32-gnutls 3.8.13-1.hum1, +1 more
    fixed: vendor fix RHSA-2026:13274
  • Red Hat OpenShift AI 3.4 rhai/base-image-neuron-rhel9 1790703542
    fixed: vendor fix RHSA-2026:74674
  • Red Hat OpenShift Container Platform 4.12 rhcos 412.86.202608241157
    fixed: vendor fix RHSA-2026:59831
  • Red Hat OpenShift Container Platform 4.16 rhcos 416.94.202608150307
    fixed: vendor fix RHSA-2026:56853
  • Red Hat OpenShift Container Platform 4.17 rhcos 417.94.202608250221
    fixed: vendor fix RHSA-2026:60019
  • Red Hat OpenShift Container Platform 4.18 rhcos 418.94.202608142238
    fixed: vendor fix RHSA-2026:57483
  • Red Hat OpenShift Container Platform 4.19 rhcos 4.19.9.6.202607151909
    fixed: vendor fix RHSA-2026:40762

4 more fixed, 19 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat OpenShift Container Platform 4.12
  • Red Hat Red Hat OpenShift Container Platform 4.16
  • Red Hat Red Hat OpenShift Container Platform 4.17
  • Red Hat Red Hat OpenShift Container Platform 4.18
  • Red Hat Red Hat OpenShift Container Platform 4.19
  • Red Hat Red Hat OpenShift Container Platform 4.20
  • Red Hat Red Hat OpenShift Container Platform 4.21
  • Red Hat Red Hat OpenShift Container Platform 4.22
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.17
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.18
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.20
  • Red Hat Red Hat Discovery 2
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat OpenShift AI 3.4
  • Red Hat Red Hat Update Infrastructure 5
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat OpenShift Container Platform 4
  • Red Hat Red Hat OpenShift Container Platform 5

Classification

Weakness
  • CWE-295 Improper Certificate Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.