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HIGH · 7.8

CVE-2026-50257

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 attacke...

Vulnerability 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.

CVSS 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
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH

Affected Products

VendorProductVersions
X.OrgX Server< 21.1.23
X.OrgXwayland< 24.1.12
RedhatEnterprise Linux7.0

Related Weaknesses (CWE)

CWE-416

References

FAQ

What is CVE-2026-50257?

CVE-2026-50257 is a vulnerability with a CVSS score of 7.8 (HIGH). 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 attacke...

How severe is CVE-2026-50257?

CVE-2026-50257 has been rated HIGH with a CVSS base score of 7.8/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-50257?

Check the references section above for vendor advisories and patch information. Affected products include: X.Org X Server, X.Org Xwayland, Redhat Enterprise Linux.