CVE-2026-50256

high

Published 2026-06-05 · Modified 2026-06-05

💬 Discuss on Community ✚ Propose mitigation

CVSS v3

7.8

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

CVSS v4 NEW

—

not yet in upstream

VIR risk

7.8

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.

Predictions

Exploit likelihood

75%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

Mitigation details

Source: Debian Security Tracker · View original ↗ · DFSG

CVE-2026-50256 NameCVE-2026-50256 DescriptionFont Alias Stack-based Buffer Overflow SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) Debian Bugs1138680, 1138703 Vulnerable and fixed packages The table below lists information on source packages. Source PackageReleaseVersionStatus…

CVE-2026-50256

Name	CVE-2026-50256
Description	Font Alias Stack-based Buffer Overflow
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1138680, 1138703

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xorg-server (PTS)	bullseye	2:1.20.11-1+deb11u13	vulnerable
	bullseye (security)	2:1.20.11-1+deb11u17	vulnerable
	bookworm	2:21.1.7-3+deb12u12	vulnerable
	bookworm (security)	2:21.1.7-3+deb12u11	vulnerable
	trixie	2:21.1.16-1.3+deb13u2	vulnerable
	trixie (security)	2:21.1.16-1.3+deb13u1	vulnerable
	forky	2:21.1.22-1	vulnerable
	sid	2:21.1.23-1	fixed
xwayland (PTS)	bookworm	2:22.1.9-1	vulnerable
	trixie	2:24.1.6-1	vulnerable
	forky	2:24.1.11-1	vulnerable
	sid	2:24.1.12-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
xorg-server	source	(unstable)	2:21.1.23-1			1138680
xwayland	source	(unstable)	2:24.1.12-1			1138703

Notes

[trixie] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)
[bookworm] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)
https://www.openwall.com/lists/oss-security/2026/06/02/1
https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07

Home - Debian Security - Source (Git)

Apply commands

text fix

Notes

[trixie] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)[bookworm] - xwayland <ignored> (Minor issue; Xwayland shouldn't be running as root)https://www.openwall.com/lists/oss-security/2026/06/02/1https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Debian Mixed 5 releases

Version	Status	Fixed in
trixie	Affected	—
sid	Fixed	`2:21.1.23-1`
forky	Affected	—
bullseye	Affected	—
bookworm	Affected	—

References

CWEs

CWE-121

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.