In AccessControlContext.combineWithPrivilegedContext, if this.context is null and pacc.context is null and pacc.combiner is not null, goCombiner is called, which in turn calls the combiner, which in all likelihood will return null, which gets passed to the AccessControlContext private constructor, which will attempt to clone null and throw NullPointerException.

bob.scheifler@East 2000-07-12

Another way this can happen is if this.context is null and pacc.context is an empty array and pacc.combiner is not null. Normally the context can't be an empty array, but the public constructor that takes a ProtectionDomain[] allows it (in fact it disallows null), and the JAAS Subject.doAsPrivileged will call this constructor with an empty array if a null ACC is passed to it.

bob.scheifler@East 2000-07-12