CVE-2026-42013
Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name
CVSS Score
8.2
EPSS Score
0.4%
EPSS Percentile
35th
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.
| CWE | CWE-295 |
| Vendor | red hat |
| Product | red hat enterprise linux 10 |
| Published | May 26, 2026 |
| Last Updated | Jul 22, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None
Affected Versions
Red Hat / Red Hat Enterprise Linux 10
All versions affected Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support
All versions affected Red Hat / Red Hat Enterprise Linux 7 Extended Lifecycle Support
All versions affected Red Hat / Red Hat Enterprise Linux 8
All versions affected Red Hat / Red Hat Enterprise Linux 8
All versions affected Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
All versions affected Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
All versions affected Red Hat / Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
All versions affected Red Hat / Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
All versions affected Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
All versions affected Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
All versions affected Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
All versions affected Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
All versions affected Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service
All versions affected Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service
All versions affected Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
All versions affected Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
All versions affected Red Hat / Red Hat Enterprise Linux 9
All versions affected Red Hat / Red Hat Enterprise Linux 9
All versions affected Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
All versions affected Red Hat / Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
All versions affected Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support
All versions affected Red Hat / Red Hat OpenShift Container Platform 4.19
All versions affected Red Hat / Red Hat Discovery 2
All versions affected Red Hat / Red Hat Discovery 2
All versions affected Red Hat / Red Hat Hardened Images
All versions affected Red Hat / Red Hat Update Infrastructure 5
All versions affected Red Hat / Red Hat Update Infrastructure 5
All versions affected Red Hat / Red Hat Update Infrastructure 5
All versions affected Red Hat / Red Hat Update Infrastructure 5
All versions affected Red Hat / Red Hat Enterprise Linux 6
All versions affected Red Hat / Red Hat OpenShift Container Platform 4
All versions affected References
access.redhat.com: https://access.redhat.com/errata/RHSA-2026:13274 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:20611 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:20612 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:20613 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:26319 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:26409 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:29197 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:30004 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:30849 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:30850 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:32962 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:33125 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:40762 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:41921 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:43575 access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-42013 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2467448 gnutls.org: https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-8
Credits
Red Hat would like to thank Haruto Kimura (Stella) and Joshua Rogers (AISLE Research Team) for reporting this issue.