Vulnerability in GNU Gnutls
CVE-2026-3833
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.009 (58.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.009 · change: +0.003
Affected products
- GNU Gnutls
- Red Hat Discovery 2 — versions 1782159791, 1782166952
- Red Hat Enterprise Linux 10 — versions 0:3.8.10-4.el10_2
- Red Hat Enterprise Linux 10.0 Extended Update Support — versions 0:3.8.9-9.el10_0.19
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 7 Extended Lifecycle Support — versions 0:3.3.29-9.el7_9.2
- Red Hat Enterprise Linux 8 — versions 0:3.6.16-8.el8_10.6
- Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support — versions 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
- Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On — versions 0:3.6.14-10.el8_4.1, 0:4.13-3.el8_4.1
Weakness classification (CWE)
References
- access.redhat.com/errata/RHSA-2026:13274 (vendor-advisory, Third Party Advisory, Issue Tracking)
- access.redhat.com/security/cve/CVE-2026-3833 (Third Party Advisory, vdb-entry)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Third Party Advisory, Issue Tracking)
- gitlab.com/gnutls/gnutls/-/issues/1803 (Exploit, Issue Tracking, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:20611 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:20613 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:20612 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:26319 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:26409 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:29197 (vendor-advisory)
Frequently asked questions
- What is CVE-2026-3833?
- CVE-2026-3833 is a medium-severity vulnerability in GNU Gnutls, classified under Improper Handling of Case Sensitivity. CVSS score: 6.5/10. Published 2026-04-30.
- How severe is CVE-2026-3833?
- Medium severity. CVSS v3 base score is 6.5 out of 10.