CVE-2026-50258

High

Description

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. The X server has multiple stack buffers sized XkbMaxShiftLevel * XkbNumKbdGroups but CheckKeyTypes() does not verify or clamp non-canonical key types to XkbMaxShiftLevel. A client can change key types to excessive shift levels and trigger stack overflows. This is caused by an incomplete fix of CVE-2025-26597. This may be used to crash the server, or for privilege escalation if the X server runs as root.

SeverityHigh

CVSS7.8

Exploit probability—

Product

X.org Xwayland

PublishedJun 5, 2026

First seenJun 5, 2026

Weakness typeCWE-121CWE-121

How to fix

Update

x.org xwayland24.1.12 or later
x.org x_server21.1.23 or later

Patches

gitlab.freedesktop.org/xorg/xserver/-/commit/543e108516428fc8c3bea91d6563ad266f9a801e

Vendor advisories

Affected products

Product	Affected versions	Fixed in
x.org xwayland	v < 24.1.12	24.1.12
x.org x_server	v < 21.1.23	21.1.23
redhat enterprise_linux	7.0, 8.0, 9.0, 10.0	—

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