CVE-2025-26601: Xorg: xwayland: use-after-free in syncinittrigger()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-25 · updated 2026-06-29
Weakness: CWE-416

Description

A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are evaluated one after the other, changing the trigger values as requested, and eventually, SyncInitTrigger() is called. If one of the changes triggers an error, the function will return early, not adding the new sync object, possibly causing a use-after-free when the alarm eventually triggers.

Affected products

Red Hat Enterprise Linux: 7.0, 8.0, 9.0
Kaspersky TigerVNC: all versions
xorg-x11-server: before 21.1.16 — fixed in 21.1.16
X.Org xwayland: before 24.1.6 — fixed in 24.1.6

How to fix

Upgrade to a fixed version: xorg-x11-server 21.1.16; X.Org xwayland 24.1.6. Check the vendor advisory for mitigations.

References

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