Report: CVE-2026-33308 - mod_gnutls missing key purpose check in client certificate verification - Guide

Report: CVE-2026-33308 - mod_gnutls missing key purpose check in client certificate verification - Guide

CVE ID :CVE-2026-33308 Published : March 24, 2026, 3:16 a.m. | 44 minutes ago Description :Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. Prior to version 0.13.0, code for client certificate verification did not check the key purpose as set in the Extended Key Usage extension. An attacker with access to the private key for a valid certificate issued by a CA trusted for TLS client authentication but designated for a different purpose could have used that certificate to improperly access resources requiring TLS client authentication. Server configurations that do not use client certificates (`GnuTLSClientVerify ignore`, the default) are not affected. The problem has been fixed in version 0.13.0 by rewriting certificate verification to use `gnutls_certificate_verify_peers()`, and requiring key purpose id-kp-clientAuth (also known as `tls_www_client` in GnuTLS) by default if the Extended Key Usage extension is present. The new `GnuTLSClientKeyPurpose` option allows overriding the expected key purpose if needed (please see the manual for details). Behavior for certificates without an Extended Key Usage extension is unchanged. If dedicated (sub-)CAs are used for issuing TLS client certificates only (not for any other purposes) the issue has no practical impact. Severity: 6.8 | MEDIUM Visit the link for more details, such as CVSS details, affected products, timeline, and more...

CVE Details

Severity
MEDIUM
Published
March 24, 2026
Affected Product: Apache