libxml2: dict corruption caused by entity reference cycles

A flaw was found in libxml2. When a reference cycle is detected in the XML entity cleanup function the XML entity data can be stored in a dictionary. In this case, the dictionary becomes corrupted resulting in logic errors, including memory errors like double free...

Double Free

libxml2 is vulnerable to double free. When a reference cycle is detected in the XML entity cleanup function the XML entity data can be stored in a dictionary which may become corrupted resulting in logic errors, including memory errors like double free...