Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: use-after-free in syncchangecounter()

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Summary

CVECVE-2026-50261
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-05 12:16:39 UTC
Updated2026-06-05 13:27:38 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-416 | CWE-416 Use After Free

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Enterprise Linux 10 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 8 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 8 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 9 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 9 Not specified Not specified

References

ReferenceSourceLinkTags
lists.x.org/archives/xorg-announce/2026-June/003702.html [email protected] lists.x.org
gitlab.freedesktop.org/xorg/xserver/-/commit/bdd7bf57af208b1ddf57d4683d67104443b44812 [email protected] gitlab.freedesktop.org
redhat.atlassian.net/browse/PSIRTSUPT-16950 [email protected] redhat.atlassian.net
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
access.redhat.com/security/cve/CVE-2026-50261 [email protected] access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Upstream acknowledges Anonymous (Trend Micro Zero Day Initiative) as the original reporter. (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-05-15T03:14:46.000ZReported to Red Hat.
CNA2026-06-02T00:00:00.000ZMade public.
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