Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangecounter()

Summary

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.

Timeline

1. Jun 5, 2026, 12:00 AM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

2. Jun 5, 2026, 10:36 AM UTCCVE published
3. Sep 28, 2026, 11:46 AM UTCRecord last updated

Affected versions

• xorg-x11-server-Xwayland

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• xorg-x11-server

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• xorg-x11-server

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

• xorg-x11-server-Xwayland

  Version range not reported

• tigervnc

  Version range not reported

• xorg-x11-server

  Version range not reported

References 25