CVE-2026-34001

A flaw was found in the X.Org X server. This use-after-free vulnerability occurs in the XSYNC fence triggering logic, specifically within the miSyncTriggerFence() function. An attacker with access to the X11 server can exploit this without user interaction, leading to a server crash and potentially enabling memory corruption. This could result in a denial of service or further compromise of the system.

Important: This use-after-free vulnerability in the X.Org X server's XSYNC fence triggering logic can lead to a server crash and potential memory corruption. Exploitation requires an attacker to have access to the X11 server, typically limited to local users or trusted remote connections. Systems not running the X.Org X server are not affected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, restrict access to the X11 server to trusted users and networks. If the X.Org X server is not required, consider disabling or uninstalling it. For environments where the X server is essential, running X applications within a sandboxed environment can help reduce the attack surface.