The Java Web Start implementation in Sun Java SE 6 before Update 15 allows context-dependent attackers to cause a denial of service (NullPointerException) via a crafted .jnlp file, as demonstrated by the jnlp_file/appletDesc/index.html#misc test in the Technology Compatibility Kit (TCK) for the Java Network Launching Protocol (JNLP).
http://java.sun.com/javase/6/webnotes/6u15.html
http://secunia.com/advisories/37386
http://secunia.com/advisories/37460
http://security.gentoo.org/glsa/glsa-200911-02.xml
http://www.vmware.com/security/advisories/VMSA-2009-0016.html