CVE-2026-50261
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
A use-after-free vulnerability was found in the X.Org X server and Xwayland in the SyncChangeCounter() function. A client setting up multiple SyncCounters can trigger this flaw by destroying those counters via a second client connection while they are being changed.
Risk Assessment
This vulnerability may cause the X server to crash or lead to privilege escalation if the X server runs as root, posing a significant security risk to the system.
Recommendation
Immediately update the X.Org X server and Xwayland packages to a version containing the fix that addresses the use-after-free vulnerability in SyncChangeCounter().
Original NVD description (English source)
A use-after-free flaw was found in the X.Org X server and Xwayland in SyncChangeCounter(). A client that sets up multiple SyncCounters can trigger a use-after-free when destroying those counters via a second client connection while changing those counters. This may be used to crash the server, or for privilege escalation if the X server runs as root.