X.Org Server libXrender RenderQueryPictFormats Reply Heap-based Buffer Overflow Remote Code Execution Vulnerability

November 10th, 2026
ZDI-26-905 ZDI-CAN-32093

CVE ID

CVE-2026-88807

CVSS Score

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

Affected Vendors

X.Org

Affected Products

Server

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of X.Org Server. User interaction is required to exploit this vulnerability in that the target must connect to a malicious X11 server.

The specific flaw exists within the XRenderQueryFormats 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 execute code in the context of the current process.

Additional Details

X.Org has issued an update to correct this vulnerability. More details can be found at:
https://gitlab.freedesktop.org/xorg/lib/libxrender/-/merge_requests/19

Disclosure Timeline

  • 2026-09-02 - Vulnerability reported to vendor
  • 2026-11-10 - Coordinated public release of advisory
  • 2026-11-10 - Advisory Updated

Credit

Adam Bedard

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