7.4

CVE-2026-3833: gnu gnutls Improper Handling of Case Sensitivity

CVSS: 7.4v3.1HighModified
AliasesALPINE-CVE-2026-3833UBUNTU-CVE-2026-3833DEBIAN-CVE-2026-3833
Published 30-04-2026Last modified 14-10-2026
Open JSON

Vulnerability summary

CVE-2026-3833 is a high (CVSS 7.4) Improper Handling of Case Sensitivity vulnerability in gnu gnutls. EPSS estimates a 0.89% chance of exploitation in the next 30 days, higher than 58.7% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
40/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.4/10
010
High · v3.1 (NVD)
EPSS score
0.89%
0%100%
Low · +0.33 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1reference

Advisory lineage

Upstream 0 · Downstream 17 · Related 6
OPENSUSE-SU-2026:10691-1RHSA-2026:13274RHSA-2026:20611RHSA-2026:20612RHSA-2026:20613RHSA-2026:26409

Timeline

  1. 30-04-2026
    PublishedVulnerability first disclosed.
  2. 14-10-2026
    Last modifiedVulnerability information updated.

Description

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.89%

Chance of exploitation in the next 30 days

Percentile

59%

Versus all other CVEs

30-day change

+0.33 pp

From 0.56% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.89%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • referenceUnverified

    Exploit Reference (gitlab.com)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Redhat3 products
Alpine1 product
  • gnutls< 3.8.13-r0
Debian1 product
  • gnutls28< 3.7.9-2+deb12u7 | < 3.8.9-3+deb13u4 | < 3.8.13-1
Gnu1 product
Ubuntu1 product
  • gnutls28< 3.4.10-4ubuntu1.9+esm3 | < 3.5.18-1ubuntu1.6+esm3 | < 3.6.13-2ubuntu1.12+esm2 | < 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

5 vendors · 7 products

References

42 links
Show all 42 references