In the X.Org X server before 2017-06-19, a user authenticated to
an X Session could crash or execute code in the context of the X
Server by exploiting a stack overflow in the endianness conversion
of X Events.
Uninitialized data in endianness conversion in the XEvent handling
of the X.Org X Server before 2017-06-19 allowed authenticated
malicious users to access potentially privileged data from the X
server.