libxml2: Heap-based buffer overread in xmlPArserPrintFileContextInternal

The xmlPArserPrintFileContextInternal function in libxml2 before 2.9.4, as used in Apple iOS before 9.3.2, OS X before 10.11.5, tvOS before 9.2.1, and watchOS before 2.2.1, allows remote attackers to cause a denial of service heap-based buffer over-read via a crafted XML document...