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Description

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.

PUBLISHED Reserved 2026-06-04 | Published 2026-06-05 | Updated 2026-06-06 | Assigner redhat




HIGH: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem types

Use After Free

Product status

Default status
affected

Default status
unknown

Default status
affected

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affected

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affected

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affected

Default status
affected

Timeline

2026-05-15:Reported to Red Hat.
2026-06-02:Made public.

Credits

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

References

access.redhat.com/security/cve/CVE-2026-50261 vdb-entry

bugzilla.redhat.com/show_bug.cgi?id=2485386 (RHBZ#2485386) issue-tracking

gitlab.freedesktop.org/...57af208b1ddf57d4683d67104443b44812

lists.x.org/archives/xorg-announce/2026-June/003702.html

redhat.atlassian.net/browse/PSIRTSUPT-16950

cve.org (CVE-2026-50261)

nvd.nist.gov (CVE-2026-50261)

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