# CVE-2026-3833: GnuTLS policy bypass in nameConstraints comparison

Source: https://junglewise.ai/threats/cve-2026-3833-gnutls-policy-bypass-in-nameconstraints-comparison  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-30. Updated: 2026-05-27  
License: CC BY 4.0 with a link back

CVE-2026-3833 · Severity: medium · CVSS 6.5 · Published 2026-04-30

GnuTLS is a widely used security library that helps applications establish secure encrypted connections. A flaw was found where the library incorrectly validates digital certificates due to how it handles uppercase and lowercase letters in domain names and email addresses. An attacker could use a specially crafted certificate to bypass security policies, potentially leading to unauthorized access to sensitive data or systems.

## Quick answers

**Is CVE-2026-3833 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-3833 being exploited in the wild.

**How severe is CVE-2026-3833?** Medium severity, with a CVSS score of 6.5, published 30 April 2026.

**Which products and versions are affected?** GNU GnuTLS 3.8.13-1, 3.6.16-8.el8_10.6; Red Hat Enterprise Linux 6.0, 7.0, 8.0, 9.0, 10.0; Red Hat Openshift Container Platform 4.0.

**Is there a fix for CVE-2026-3833?** A patch was published on 2026-05-02: Red Hat released security advisory RHSA-2026:13274 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-3833 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-3833?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A vulnerability exists in GnuTLS due to improper handling of case sensitivity (CWE-178) during X.509 certificate validation. The library performs case-sensitive comparisons using memcmp for nameConstraints labels, specifically for dNSName and rfc822Name constraints within excludedSubtrees or permittedSubtrees, without an ASCII case-folding step. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN) that differ from the defined constraints. This results in a policy bypass where a certificate that should be rejected is accepted. Patches have been released by Red Hat and GnuTLS upstream to address this issue.

## Affected products

- GNU GnuTLS 3.8.13-1, 3.6.16-8.el8_10.6
- Red Hat Enterprise Linux 6.0, 7.0, 8.0, 9.0, 10.0
- Red Hat Openshift Container Platform 4.0

## Timeline

- 2026-03-09: disclosed: Initial report in Red Hat Bugzilla
- 2026-04-30: advisory: NVD and Red Hat published initial CVE details
- 2026-05-02: patched: Red Hat released security advisory RHSA-2026:13274

## References

- [https://access.redhat.com/errata/RHSA-2026:13274](https://access.redhat.com/errata/RHSA-2026:13274)
- [https://access.redhat.com/errata/RHSA-2026:20611](https://access.redhat.com/errata/RHSA-2026:20611)
- [https://access.redhat.com/security/cve/CVE-2026-3833](https://access.redhat.com/security/cve/CVE-2026-3833)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2445763](https://bugzilla.redhat.com/show_bug.cgi?id=2445763)
- [https://gitlab.com/gnutls/gnutls/-/issues/1803](https://gitlab.com/gnutls/gnutls/-/issues/1803)