CVE-2026-33308
Description
A flaw was found in mod_gnutls, a TLS module for Apache HTTPD. Prior to version 0.13.0, the module's client certificate verification process did not properly validate the key purpose specified in the Extended Key Usage (EKU) extension. This oversight could allow a remote attacker, possessing a valid client certificate issued by a trusted Certificate Authority (CA) but intended for a different use, to improperly access resources that require TLS client authentication. This vulnerability enables unauthorized access to protected resources.
Statement
Red Hat Product Security has determined that this vulnerability does not affect any currently supported Red Hat product. This assessment may evolve based on further analysis and discovery. For more information about this vulnerability and the products it affects, please see the linked references.
Mitigation
The vulnerability can be mitigated by ensuring that Certificate Authorities (CAs) used for issuing TLS client certificates are dedicated solely for that purpose. If client certificate authentication is not strictly required, disable client certificate verification in the `mod_gnutls` configuration by setting `GnuTLSClientVerify ignore`. This is the default configuration and prevents exploitation. If `mod_gnutls` is reloaded or restarted, the new configuration will take effect.
Understanding the Weakness (CWE)
Integrity,Authentication
Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity
When a certificate is invalid or malicious, it might allow an attacker to spoof a trusted entity by interfering in the communication path between the host and client. The product might connect to a malicious host while believing it is a trusted host, or the product might be deceived into accepting spoofed data that appears to originate from a trusted host.
Frequently Asked Questions
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