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CVE-2026-50258

A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland.

Impact

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.

Affected products

VendorProductAffected versions
X.OrgX Server
before 21.1.23
X.OrgXwayland
before 24.1.12
RedhatEnterprise Linux
Versions 7.0, 8.0, 9.0, 10.0

Weakness classification

CWE-121

References