CVE-2026-50257
Modified Modified - Updated After Analysis
Use-After-Free in X.Org X Server and Xwayland

Publication date: 2026-06-05

Last updated on: 2026-06-25

Assigner: Red Hat, Inc.

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 Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-06-05
Last Modified
2026-06-25
Generated
2026-06-25
AI Q&A
2026-06-05
EPSS Evaluated
2026-06-24
NVD
CVE-2026-50257
EUVD
EUVD-2026-34812
Affected Vendors & Products
Showing 6 associated CPEs
Vendor Product Version / Range
redhat enterprise_linux 7.0
redhat enterprise_linux 8.0
redhat enterprise_linux 9.0
redhat enterprise_linux 10.0
x.org x_server to 21.1.23 (exc)
x.org xwayland to 24.1.12 (exc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Compliance Impact

The provided information does not specify how this vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

Executive Summary

CVE-2026-50257 is a use-after-free vulnerability in the X.Org X server and Xwayland, specifically in the miSyncDestroyFence() function.

This flaw occurs when a client sets up multiple fence triggers and a second X connection destroys the fence, causing a use-after-free function pointer call.

This means that memory that has already been freed is accessed again, which can lead to unexpected behavior.

Impact Analysis

An attacker connected to the X server can exploit this vulnerability to crash the server.

If the X server is running with root privileges, the attacker may also achieve privilege escalation, gaining higher-level access than intended.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade the affected components to fixed versions where the issue has been resolved.

  • Upgrade xorg-x11-server to version 21.1.23 or later.
  • Upgrade xorg-x11-server-Xwayland to version 24.1.12 or later.

These updates fix the use-after-free flaw in the miSyncDestroyFence() function that can be exploited by a client connected to the X server.

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-50257. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart