X.org libXt 1.1.3 and earlier does not check the return value of the XGetWindowProperty function, which allows X servers to trigger use of an uninitialized pointer and memory corruption via vectors related to the (1) ReqCleanup, (2) HandleSelectionEvents, (3) ReqTimedOut, (4) HandleNormal, and (5) HandleSelectionReplies functions.
Buffer overflow in X.org libXt 1.1.3 and earlier allows X servers to cause a denial of service (crash) and possibly execute arbitrary code via crafted length or index values to the _XtResourceConfigurationEH function.