CVE-2026-50257

High

Description

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.

SeverityHigh

CVSS7.8

Exploit probability—

Product

X.org Xwayland

PublishedJun 5, 2026

First seenJun 5, 2026

Weakness typeCWE-416Use after free

How to fix

Update

x.org xwayland24.1.12 or later
x.org x_server21.1.23 or later

Patches

gitlab.freedesktop.org/xorg/xserver/-/commit/f5abfb61994471023d8c6470428c8e30c411cc0b

Vendor advisories

Affected products

Product	Affected versions	Fixed in
x.org xwayland	v < 24.1.12	24.1.12
x.org x_server	v < 21.1.23	21.1.23
redhat enterprise_linux	7.0, 8.0, 9.0, 10.0	—

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