CVE-2026-50258 | BDVDB-2026-338313 Detail

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.

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Exploit#

History#

1. Version 12026-06-05Record published in the CVE List.
2. Version 22026-11-04Most recent update recorded in the CVE List.