Use-After-Free Vulnerability in X.Org X Server and Xwayland
CVE-2026-50257

7.8HIGH

Key Information:

Vendor

Red Hat
Status
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 10.0 Extended Update Support
Red Hat Enterprise Linux 7 Extended Lifecycle Support
Red Hat Enterprise Linux 8
Vendor
CVE Published:
5 June 2026

What is CVE-2026-50257?

A use-after-free vulnerability exists in the X.Org X server and Xwayland within the miSyncDestroyFence() function. When a client sets up multiple fence triggers, this flaw can be exploited by an attacker who connects to the X server to create a fence and then waits for its completion. If another X connection destroys this fence while it is still in use, it can lead to accessing freed memory, resulting in a potential server crash or allowing unauthorized privilege escalation if the server is running with elevated privileges.

Affected Version(s)

Red Hat Enterprise Linux 10 0:24.1.9-4.el10_2.2

Red Hat Enterprise Linux 10.0 Extended Update Support 0:24.1.5-6.el10_0.1

Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.20.4-35.el7_9

References

https://access.redhat.com/errata/RHSA-2026:26562
vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:26566
vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:26590
vendor-advisoryx_refsource_REDHAT

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

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