X.Org Server ComputeScaledProperties Heap-based Buffer Overflow Privilege Escalation Vulnerability

July 15th, 2026
ZDI-26-408 ZDI-CAN-30560

CVE ID

CVE-2026-56003

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 ComputeScaledProperties function. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length, heap-based 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/lib/libxfont/-/commit/dff957a5158da038a282a59a31fe736702732939

Disclosure Timeline

  • 2026-05-29 - Vulnerability reported to vendor
  • 2026-07-15 - Coordinated public release of advisory
  • 2026-07-15 - Advisory Updated

Credit

Anonymous

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