CVE-2026-42012: gnutls28 Improper Certificate Validation

CVSS: 7.1v3.1HighAwaiting analysis

AliasesALPINE-CVE-2026-42012UBUNTU-CVE-2026-42012DEBIAN-CVE-2026-42012

Published 26-05-2026Last modified 14-10-2026

Vulnerability summary

CVE-2026-42012 is a high (CVSS 7.1) Improper Certificate Validation vulnerability in gnutls28. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 40.6% of scored vulnerabilities.

Overall risk

28/100

0100

Medium · default modelHow is this calculated?

CVSS score

7.1/10

010

High · v3.1 (CVE.org)

EPSS score

0.49%

0%100%

Low · +0.13 pp in 30 days

KEVNot listedIn no KEV catalog

RansomwareNone recordedNo known use recorded

Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 15 · Related 4

OPENSUSE-SU-2026:10691-1 RHSA-2026:13274 RHSA-2026:20611 RHSA-2026:20612 RHSA-2026:20613 RHSA-2026:26409+10 more

Timeline

26-05-2026
PublishedVulnerability first disclosed.
14-10-2026
Last modifiedVulnerability information updated.

Description

A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.

CVSS metrics

5 scores · 5 sources · 1 version

v3.17.1

EPSS trend

Probability

0.49%

Chance of exploitation in the next 30 days

Percentile

41%

Versus all other CVEs

30-day change

+0.13 pp

From 0.35% on 19-09-2026

19-09-202619-10-2026

EPSS score

0.49%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

CWE-295Improper Certificate ValidationThe product does not validate, or incorrectly validates, a certificate.

Affected systems

Alpine1 product

gnutls< 3.8.13-r0

Debian1 product

gnutls28< 3.7.9-2+deb12u7 | < 3.8.9-3+deb13u4 | < 3.8.13-1

Ubuntu1 product

gnutls28< 3.4.10-4ubuntu1.9+esm4 | < 3.5.18-1ubuntu1.6+esm4 | < 3.6.13-2ubuntu1.12+esm3 | < 3.7.3-4ubuntu1.9 | All versions (No fix recorded) | < 3.7.3-4ubuntu1.9+Fips1 | < 3.8.3-1.1ubuntu3.6 | < 3.8.3-1.1ubuntu3.6+Fips1.2 | < 3.8.9-3ubuntu2.2 | < 3.8.12-2ubuntu1.1

3 vendors · 3 products