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

7.8HIGH

Key Information:

Vendor

Red Hat
Status
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8
Vendor
CVE Published:
5 June 2026

What is CVE-2026-50258?

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.

References

https://access.redhat.com/security/cve/CVE-2026-50258
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2485383
issue-trackingx_refsource_REDHAT
https://gitlab.freedesktop.org/xorg/xserver/-/commit/543e...

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Upstream acknowledges Anonymous (Trend Micro Zero Day Initiative) as the original reporter.
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