Vulnerability Report

CVE-2026-55999

Title: Heap Buffer Overflow in xorg-server and xwayland via PCX Fonts

Memory Corruption

Proof Of Concept

No public PoC currently indexed for CVE-2026-55999.

CWE Category CWE-122

Published Date Jul 08, 2026

Modified Date Jul 09, 2026

Exploit Status Not Found

Score 8.5 CVSS v3.1

Exploit Probability (EPSS)

0.27%

Vulnerability Summary

CVE-2026-55999: 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.

Impacted Vendors

x.org 2

Reference Links

https://gitlab.freedesktop.org/xorg/xserver/-/commit/fbf7bac22e2c6bd627fb042742a23318263edae1 https://www.openwall.com/lists/oss-security/2026/07/08/2

CVSS v3.1

Source Entity [email protected]

Severity HIGH

7.8

Attack Vector

LOCAL

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1

Source Entity [email protected]

Severity HIGH

8.5

Attack Vector

NETWORK

Complexity

HIGH

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

CHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Associated Attack Patterns (CAPEC)

Total: Patterns