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HIGH

CVE-2026-42013

CVSS v3

8.2

HIGH

EPSS Score

0.6 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • CVE-2026-42013 Red Hat Product Security876 products fixed · 5 known affected

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

    gnutls as a component of Red Hat Enterprise Linux 6 · gnutls-devel as a component of Red Hat Enterprise Linux 6 · gnutls-guile as a component of Red Hat Enterprise Linux 6

  • RHSA-2026:82888 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.17.2

  • RHSA-2026:82857 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82372 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82354 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

  • RHSA-2026:82347 Red Hat Product Security8 products fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

24 more advisories

Full record on NVD

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
Published
2026-05-26
Last Modified
2026-07-24
MSRC Title
Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name

Frequently asked questions

What is 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.

Is CVE-2026-42013 actively exploited?

Active exploitation of CVE-2026-42013 has not been confirmed. Its EPSS score was 0.6% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-42013?

CVE-2026-42013 has a CVSS v3 base score of 8.2 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N.

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