Out-of-bounds Read vulnerability in the XKB geometry processing of the X.Org X server. The issue is located in CheckSetGeom(), where bounds checking is performed using only the first key name of each alias entry (alias vs. real key name). Because the second name is not properly validated, XkbAddGeomKeyAlias may read uninitialized or out-of-bounds memory when processing a crafted request. An attacker who can connect to the X11 server (locally or via forwarded remote sessions) can trigger this without user interaction, potentially leaking memory contents and/or causing a crash.