🛡️ CVE-2026-50256 on Debian — xorg-server

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.

Distribution advisory

This page covers CVE-2026-50256 as tracked by Debian, for the package xorg-server. The fix is available in version 2:21.1.23-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

DEBIAN-CVE-2026-50256 is classified as CWE-121: Stack-based Buffer Overflow. An oversized write to a stack buffer overwrites saved state such as return addresses, which can redirect execution.

Affected software

DEBIAN-CVE-2026-50256 is recorded against 2 packages.

  • xorg-server (fixed in 2:21.1.23-1)
  • xwayland (fixed in 2:24.1.12-1)

Timeline and source

Published on 5 June 2026 and last revised on 6 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2026-50256 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-06-05
Updated 2026-08-12
Modified 2026-08-06
Fix URL N/A

Affected Packages

Software From version Fixed in
xorg-server — 2:21.1.23-1
xwayland — 2:24.1.12-1

Site Security Check

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DEBIAN-CVE-2026-50256 is rated CVSS 7.8 High. BotEraser scans your installation against known CVE records and tells you whether this vulnerability applies to the versions you actually run.

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