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

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Summary

CVECVE-2026-42013
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-26 22:16:42 UTC
Updated2026-06-01 21:16:44 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from [email protected]

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

EPSS: 0.000330000 probability, percentile 0.101900000 (date 2026-05-31)

Problem Types: CWE-1284 | CWE-1284 Improper Validation of Specified Quantity in Input

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
3.1CNACVSS8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Enterprise Linux 10 unaffected 0:3.8.10-4.el10_2 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:3.6.16-8.el8_10.6 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 8 unaffected 0:3.6.16-8.el8_10.6 * rpm Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 9 Not specified Not specified
CNA Red Hat Red Hat Hardened Images Not specified Not specified
CNA Red Hat Red Hat OpenShift Container Platform 4 Not specified Not specified

References

ReferenceSourceLinkTags
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
access.redhat.com/errata/RHSA-2026:20613 [email protected] access.redhat.com
access.redhat.com/security/cve/CVE-2026-42013 [email protected] access.redhat.com
access.redhat.com/errata/RHSA-2026:20611 [email protected] access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

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

Additional Advisory Data

SourceTimeEvent
CNA2026-05-06T19:47:00.134ZReported to Red Hat.
CNA2026-04-29T00:00:00.000ZMade public.
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