XMLScanner.java in Apache Xerces2 Java, as used in Sun Java Runtime Environment (JRE) in JDK and JRE 6 before Update 15 and JDK and JRE 5.0 before Update 20, and in other products, allows remote attackers to cause a denial of service (infinite loop and application hang) via malformed XML input, as demonstrated by the Codenomicon XML fuzzing framework.