CVE-2026-50261

EUVD-2026-34817
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
7.8 HIGH
LOCAL
LOW
LOW
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Awaiting analysis
This vulnerability is currently awaiting analysis.
Base Score
CVSS 3.x
EPSS Score
Percentile: 1%
Debian logo
Debian Releases
Debian Product
Codename
xorg-server
bookworm
vulnerable
bookworm (security)
vulnerable
bullseye
vulnerable
bullseye (security)
vulnerable
forky
vulnerable
sid
2:21.1.23-1
fixed
trixie
vulnerable
trixie (security)
vulnerable
xwayland
bookworm
ignored
forky
vulnerable
sid
2:24.1.12-1
fixed
trixie
ignored
Common Weakness Enumeration
Vulnerability Media Exposure
References
https://access.redhat.com/security/cve/CVE-2026-50261
https://bugzilla.redhat.com/show_bug.cgi?id=2485386
https://gitlab.freedesktop.org/xorg/xserver/-/commit/bdd7bf57af208b1ddf57d4683d67104443b44812
https://lists.x.org/archives/xorg-announce/2026-June/003702.html
https://redhat.atlassian.net/browse/PSIRTSUPT-16950