xterm, Eterm, and rxvt allow an attacker to cause a denial of service by embedding certain escape characters which force the window to be resized.
libX11 X library allows remote attackers to cause a denial of service via a resource mask of 0, which causes libX11 to go into an infinite loop.
libICE in XFree86 allows remote attackers to cause a denial of service by specifying a large value which is not properly checked by the SKIP_STRING macro.