expat -- denial of service vulnerability on malformed input

Gustavo Grieco reports:

The Expat XML parser mishandles certain kinds of malformed input
documents, resulting in buffer overflows during processing and error
reporting. The overflows can manifest as a segmentation fault or as
memory corruption during a parse operation. The bugs allow for a
denial of service attack in many applications by an unauthenticated
attacker, and could conceivably result in remote code execution.