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.

Score
CVSS 3.1 7.8 High
Status
Modified - secalert@redhat.com
Published
2026-06-05
Last modified
2026-09-28
Weaknesses
CWE-121

Affected products

References

 
 
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