CVE-2026-34002 Details

A vulnerability allowing out-of-bounds read has been identified in the X.Org X server, specifically in the handling of the XKB (X Keyboard Extension) modifier map. This flaw arises because the CheckModifierMap() function processes data without properly validating the length of the client request. Consequently, an attacker with access to the X11 server can exploit this vulnerability by sending a malformed request that causes the server to read beyond its intended memory boundaries. This exploitation can lead to the exposure of sensitive information from memory or cause the server to crash, resulting in a denial-of-service condition.

To mitigate this vulnerability, restrict access to the X11 server. If the X.Org X server is not needed, consider disabling or uninstalling it. For systems that require the X server, limit access to trusted users and networks, which can be done by configuring 'xhost' or using firewall rules to control connections to the X server. Note that changes to the X server configuration or service may require a restart of the X server, impacting active graphical sessions.