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.
Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:HI:HA:H7.8/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HMemory Safety