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Vulnerability · Published Apr 30, 2026 · Assigned by redhat

CVE-2026-3833Gnutls: gnutls: policy bypass due to case-sensitive nameconstraints comparison

Medium 6.5

In plain English

A medium-severity security flaw in gnutls. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.6%top 52.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10gnutls3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-c++3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-c++3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-c++3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-dane3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-dane3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-dane3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-devel3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-devel3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-devel3.8.10-4.el9_8ALSA-2026:20612
AlmaLinux:10gnutls-fips3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:10gnutls-utils3.8.10-4.el10_2ALSA-2026:20613
AlmaLinux:8gnutls-utils3.6.16-8.el8_10.6ALSA-2026:20611
AlmaLinux:9gnutls-utils3.8.10-4.el9_8ALSA-2026:20612
Alpine:v3.20gnutls3.8.13-r0ALPINE-CVE-2026-3833
Alpine:v3.21gnutls3.8.13-r0ALPINE-CVE-2026-3833
Alpine:v3.22gnutls3.8.13-r0ALPINE-CVE-2026-3833
Alpine:v3.23gnutls3.8.13-r0ALPINE-CVE-2026-3833
Alpine:v3.24gnutls3.8.13-r0ALPINE-CVE-2026-3833
Debian:12gnutls283.7.9-2+deb12u7DEBIAN-CVE-2026-3833
Debian:13gnutls283.8.9-3+deb13u4DEBIAN-CVE-2026-3833
Debian:14gnutls283.8.13-1DEBIAN-CVE-2026-3833
Rocky Linux:10gnutls0:3.8.10-4.el10_2RLSA-2026:20613
Rocky Linux:8gnutls0:3.6.16-8.el8_10.6RLSA-2026:20611
Rocky Linux:9gnutls0:3.8.10-4.el9_8RLSA-2026:20612
Ubuntu:22.04:LTSgnutls283.7.3-4ubuntu1.9UBUNTU-CVE-2026-3833
Ubuntu:24.04:LTSgnutls283.8.3-1.1ubuntu3.6UBUNTU-CVE-2026-3833
Ubuntu:25.10gnutls283.8.9-3ubuntu2.2UBUNTU-CVE-2026-3833
Ubuntu:26.04:LTSgnutls283.8.12-2ubuntu1.1UBUNTU-CVE-2026-3833

Affected products (as reported)

VendorProductVersions
gnutls 0 – before 3.8.13
Red Hat Red Hat Enterprise Linux 10 see references
Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support see references
Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 8 see references
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support see references
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On see references
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service see references
Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service see references
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9 see references
Red Hat Red Hat Enterprise Linux 9 see references
Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions see references
Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support see references
Red Hat Red Hat OpenShift Container Platform 4.12 see references
Red Hat Red Hat OpenShift Container Platform 4.13 see references
Red Hat Red Hat OpenShift Container Platform 4.14 see references
Red Hat Red Hat OpenShift Container Platform 4.15 see references
Red Hat Red Hat OpenShift Container Platform 4.16 see references
Red Hat Red Hat OpenShift Container Platform 4.17 see references
Red Hat Red Hat OpenShift Container Platform 4.18 see references

Weakness: CWE-178 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References