Buffer overflow in the polymorphic opcode support in the Regular Expression Engine (regcomp.c) in Perl 5.8 allows context-dependent attackers to execute arbitrary code by switching from byte to Unicode (UTF) characters in a regular expression.

Description: There exists a denial of service problem in libxml's UTF-8 decoding functions. The xmlCurrentChar() function does not check UTF-8 correctness and certain multibyte combinations can cause the library to enter an infinite loop and hang, consuming system resources. It is strongly recommended to upgrade if your application accepts arbitrary xml user input.

Provided by: The issue was originally discovered at Google by Brad Fitzpatrick and further investigated by Peter Valchev and Will Drewry. Patch and debugging by Daniel Veillard (libxml).

Acknowledgements:

Red Hat would like to thank the Google Security Team for responsibly disclosing this issue.