Home

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.

PUBLISHED Reserved 2026-06-04 | Published 2026-06-05 | Updated 2026-06-08 | Assigner redhat




HIGH: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem types

Stack-based Buffer Overflow

Product status

Default status
affected

Default status
unknown

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Timeline

2026-05-15:Reported to Red Hat.
2026-06-02:Made public.

Credits

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

References

access.redhat.com/security/cve/CVE-2026-50258 vdb-entry

bugzilla.redhat.com/show_bug.cgi?id=2485383 (RHBZ#2485383) issue-tracking

gitlab.freedesktop.org/...8516428fc8c3bea91d6563ad266f9a801e

lists.x.org/archives/xorg-announce/2026-June/003702.html

redhat.atlassian.net/browse/PSIRTSUPT-16950

cve.org (CVE-2026-50258)

nvd.nist.gov (CVE-2026-50258)

Download JSON