X.Org Server BitmapScaleBitmaps Integer Overflow Privilege Escalation Vulnerability

July 15th, 2026
ZDI-26-406 ZDI-CAN-30558

CVE ID

CVE-2026-56001

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 BitmapScaleBitmaps 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/lib/libxfont/-/commit/be0b08e2d354138d3222b4490e2a77c6ee42f778

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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