CVE-2026-50261

HIGH

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.

CVSS v3.1 Score

7.8
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
LOCAL
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Published: 6/5/2026Modified: 6/5/2026

Related Intelligence (2)

CRITICALZero Day

Patch Tuesday - June 2026

Microsoft is publishing 200 vulnerabilities on June 2026 Patch Tuesday . Microsoft is not aware of exploitation in the wild for any of these vulnerabilities, and is aware of public disclosure for three. This is similar to last month’s Patch Tuesday, however several of last month’s vulnerabilities ended up on CISA KEV in the days following their publication. So far this month, Microsoft has provide

CVE-2026-33825CVE-2026-45585
Rapid7
HIGHVulnerability

NVD HIGH: CVE-2026-50261 — A use-after-free flaw was found in the X.Org X server and Xwayland in SyncChange...

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.

CVE-2026-50261
NIST NVD

References (5)

https://access.redhat.com/security/cve/CVE-2026-50261https://bugzilla.redhat.com/show_bug.cgi?id=2485386https://gitlab.freedesktop.org/xorg/xserver/-/commit/bdd7bf57af208b1ddf57d4683d67104443b44812https://lists.x.org/archives/xorg-announce/2026-June/003702.htmlhttps://redhat.atlassian.net/browse/PSIRTSUPT-16950