Describe CVE-2012-6139.
What is CVE-2012-6139?
libxslt before 1.1.28 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via an (1) empty match attribute in a XSL key to the xsltAddKey function in keys.c or (2) uninitialized variable to the xsltDocumentFunction function in functions.c..