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

Summary

A use-after-free flaw was found in the X.Org X server and Xwayland in miSyncDestroyFence(). A client that sets up multiple fence triggers can trigger a use-after-free function pointer call. An attacker would connect to the X server to set up a fence and await that fence, then a second X connection destroys the fence, causing the use-after-free. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Timeline

1. Jun 5, 2026, 10:31 AM UTCCVE published
2. Jun 9, 2026, 12:00 AM UTCCISA SSVC assessment

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

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