CVE-2026-42013

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

At a glance

Severity: HIGH 8.2
EPSS: EPSS 0.42 % · percentile 36 (2026-10-27)
State: PUBLISHED
Published: 2026-05-26
Updated: 2026-10-14
Assigner: redhat
NVD status: Awaiting Analysis

Description

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.

Scores

Version	Score	Vector	Scored by
CVSS 3.1	HIGH 8.2	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N	redhat
CVSS 3.1	HIGH 8.2	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N	NVD · secalert@redhat.com (Secondary)

Weaknesses (CWE)

CWE-295

European references

ENISA EUVD · EUVD-2026-32011
GCVE · GCVE-0-2026-42013

CERT-FR advisories

CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
CERTFR-2026-AVI-1094 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
CERTFR-2026-AVI-0737 — Multiples vulnérabilités dans les produits Microsoft · cert.ssi.gouv.fr

Affected products

Product	Versions
gnutls	affected 0
Red Hat · Red Hat Enterprise Linux 10	unaffected 0:3.8.10-4.el10_2 < *
Red Hat · Red Hat Enterprise Linux 10.0 Extended Update Support	unaffected 0:3.8.9-9.el10_0.19 < *
Red Hat · Red Hat Enterprise Linux 7 Extended Lifecycle Support	unaffected 0:3.3.29-9.el7_9.2 < *
Red Hat · Red Hat Enterprise Linux 8	unaffected 0:3.6.16-8.el8_10.6 < *
Red Hat · Red Hat Enterprise Linux 8	unaffected 0:3.6.16-8.el8_10.6 < *
Red Hat · Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support	unaffected 0:3.6.14-10.el8_4.1 < *
Red Hat · Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support	unaffected 0:4.13-3.el8_4.1 < *
Red Hat · Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On	unaffected 0:3.6.14-10.el8_4.1 < *
Red Hat · Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On	unaffected 0:4.13-3.el8_4.1 < *
Red Hat · Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support	unaffected 0:3.6.16-5.el8_6.5 < *
Red Hat · Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support	unaffected 0:4.13-3.el8_6.2 < *
Red Hat · Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On	unaffected 0:3.6.16-5.el8_6.5 < *
Red Hat · Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On	unaffected 0:4.13-3.el8_6.2 < *
Red Hat · Red Hat Enterprise Linux 8.8 Telecommunications Update Service	unaffected 0:3.6.16-7.el8_8.4 < *
Red Hat · Red Hat Enterprise Linux 8.8 Telecommunications Update Service	unaffected 0:4.13-4.el8_8.1 < *
Red Hat · Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions	unaffected 0:3.6.16-7.el8_8.4 < *
Red Hat · Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions	unaffected 0:4.13-4.el8_8.1 < *
Red Hat · Red Hat Enterprise Linux 9	unaffected 0:3.8.10-4.el9_8 < *
Red Hat · Red Hat Enterprise Linux 9	unaffected 0:3.8.10-4.el9_8 < *

References

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)	Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD