CVE-2026-50258 HIGH

CVE-2026-50258: Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in xkb key types due to unchecked shift levels

Vendor Red Hat
Product Red Hat Enterprise Linux 6
Weakness CWE-121
Published June 5, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

7.8/10
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality High
Integrity High

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

June 5, 2026 CVE published
June 30, 2026 Record updated