🛡️ CVE-2026-55999 — x-server

🟠 CVSS 8.5 — High ✅ No Known Exploit CWE-122 NVD
8.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Local attackers with a X connection able to provide PCX fonts to the X

server xorg-server before 21.2.24 and xwayland before 24.1.13 could

cause a heap buffer overflow via SetFont due to missing glyph boundary checks.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs low-level privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-55999 is classified as CWE-122: Heap-based Buffer Overflow. A write past the end of a heap allocation corrupts allocator metadata or neighbouring objects.

Affected software

CVE-2026-55999 is recorded against 2 packages.

  • x-server (fixed in 21.2.24)
  • xwayland (fixed in 24.1.13)

Timeline and source

Published on 8 July 2026 and last revised on 9 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

gitlab.freedesktop.org
www.openwall.com

Details

Severity HIGH
CVSS Score 8.5
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
CWE CWE-122
Public Exploit ✅ No
Source NVD
Published 2026-07-08
Updated 2026-08-11
Modified 2026-07-09

Affected Packages

Software From version Fixed in
x-server — 21.2.24
xwayland — 24.1.13

Similar Threats

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