PT-2026-56334 · X.Org Foundation · Xorg-Server+1

Published 2026-07-08 · Updated 2026-07-08 · CVE-2026-55999

Positive Technologies (AI Summary)

CVSS v3.1

8.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions xorg-server versions prior to 21.2.24 xwayland versions prior to 24.1.13

Description Local attackers with an X connection can cause a heap buffer overflow by providing PCX fonts to the X server. This occurs due to missing glyph boundary checks within the SetFont() function. A heap buffer overflow is a memory corruption issue where a program writes more data to a heap-allocated buffer than it can hold, potentially leading to crashes or arbitrary code execution.

Recommendations Update xorg-server to version 21.2.24 or later. Update xwayland to version 24.1.13 or later.

Fix

Heap Based Buffer Overflow

Weakness Enumeration

CWE-122

Related Identifiers

CVE-2026-55999

Affected Products

Xorg-Server

Xwayland

References · 5

• https://gitlab.freedesktop.org/xorg/xserver/-/commit/fbf7bac22e2c6bd627fb042742a23318263edae1 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-55999 · Security Note
• https://openwall.com/lists/oss-security/2026/07/08/2 · Vendor Advisory
• https://twitter.com/infoflowcloud/status/2074826234983244080 · Twitter Post
• https://twitter.com/CVEnew/status/2074825581770772647 · Twitter Post