expat_erl.c in ejabberd before 2.1.7 and 3.x before 3.0.0-alpha-3, and exmpp before 0.9.7, does not properly detect recursion during entity expansion, which allows remote attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, a similar issue to CVE-2003-1564.