Privilege escalation via dangling fence trigger callback
Published Jun 5, 2026 · Updated Jun 5, 2026
Use-after-free in X.Org X server and Xwayland on Red Hat Enterprise Linux 7 through 10 allows local users to crash or gain root. miSyncDestroyFence() invokes CounterDestroyed callbacks while traversing fence triggers; the first callback can free sibling trigger objects, leaving later function pointers dangling. Two X connections and low-privilege access to the same X server are required; root escalation applies when the server runs as root, while other cases can terminate the display server.
Summary
What happened
Use-after-free in X.Org X server and Xwayland on Red Hat Enterprise Linux 7 through 10 allows local users to crash or gain root. miSyncDestroyFence() invokes CounterDestroyed callbacks while traversing fence triggers; the first callback can free sibling trigger objects, leaving later function pointers dangling. Two X connections and low-privilege access to the same X server are required; root escalation applies when the server runs as root, while other cases can terminate the display server.
The record
- CVE
- CVE-2026-50257
- Published
- Jun 5, 2026
- Updated
- Jun 5, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 10
- Classifications
- CWE-416, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 5, 2026CVE publishedPublication date reported by the CVE source.
- Jun 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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