X.Org Server XkbResizeKeySyms Integer Overflow Privilege Escalation Vulnerability

November 10th, 2026
ZDI-26-902 ZDI-CAN-30443

CVE ID

CVE-2026-50258

CVSS Score

7.8 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors

X.Org

Affected Products

Server

Vulnerability Details

This vulnerability allows local attackers to escalate privileges on affected installations of X.Org Server. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the XkbResizeKeySyms function. The issue results from the lack of proper validation of user-supplied data, which can result in an integer overflow before allocating a buffer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of root.

Additional Details

X.Org has issued an update to correct this vulnerability. More details can be found at:
https://gitlab.freedesktop.org/xorg/xserver/-/commit/543e108516428fc8c3bea91d6563ad266f9a801e

Disclosure Timeline

  • 2026-05-29 - Vulnerability reported to vendor
  • 2026-11-10 - Coordinated public release of advisory
  • 2026-11-10 - Advisory Updated

Credit

Anonymous

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