The XML parsing code in Sun Java Runtime Environment JDK and JRE 6 Update 3 and earlier processes external entity references even when the "external general entities" property is false, which allows remote attackers to conduct XML external entity (XXE) attacks and cause a denial of service or access restricted resources.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-0628)