CVE-2026-42011: gnutls28 Improper Certificate Validation
Vulnerability summary
CVE-2026-42011 is a high (CVSS 7.4) Improper Certificate Validation vulnerability in gnutls28. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39.6% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 17 · Related 6Timeline
- 07-05-2026PublishedVulnerability first disclosed.
- 14-10-2026Last modifiedVulnerability information updated.
Description
A flaw was found in gnutls. This vulnerability occurs because permitted name constraints were incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints. A remote attacker could exploit this to bypass critical name constraint checks during certificate validation. This bypass could lead to the acceptance of invalid certificates, potentially enabling spoofing or man-in-the-middle attacks against affected systems.
CVSS metrics
5 scores · 5 sources · 1 version- OSV · AlpineEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- OSV · UbuntuEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- NVDNIST7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS trend
Probability
0.47%
Chance of exploitation in the next 30 days
Percentile
40%
Versus all other CVEs
30-day change
0.00 pp
From 0.47% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected 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< 3.5.18-1ubuntu1.6+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
