Vulnerability record/PUBLISHED/Published May 26, 2026 21:29:32 UTC

CVE-2026-42013

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.

Base score8.2/ 10

SeverityHighCVSS 3.1

Exploitability / impact

CVSS metric breakdown

Vector-derived attributes

Base severityHigh

Attack vectorNetworkAV

Attack complexityLowAC

Privileges requiredNonePR

User interactionNoneUI

ScopeUnchangedS

Confidentiality impactLowC

Integrity impactHighI

Availability impactNoneA

CVSS vector stringCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

CVSS communicates standardized severity and impact characteristics. It does not establish whether a system is exploitable in your specific environment.

Record context

CVE Numbering Authorityredhat

Last updatedOct 30, 2026 07:29:49 UTC

PublishedMay 26, 2026 21:29:32 UTC

ReservedApr 23, 2026 11:23:46 UTC

Credits

Red Hat would like to thank Haruto Kimura (Stella) and Joshua Rogers (AISLE Research Team) for reporting this issue.