CVE-2026-50257
Use-After-Free in X.Org X Server and Xwayland
Publication date: 2026-06-05
Last updated on: 2026-06-05
Assigner: Red Hat, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| the_x.org_foundation | xorg_x11_server | to 21.1.22 (exc) |
| the_x.org_foundation | xorg_x11_server_xwayland | to 24.1.9 (exc) |
Helpful Resources
Exploitability
| 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.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 Powered Q&A
Can you explain this vulnerability to me?
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.
How can this vulnerability impact me? :
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.
What immediate steps should I take to mitigate this vulnerability?
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.