php-mbstring -- php mbstring buffer overflow vulnerability

SecurityFocus reports:

PHP is prone to a buffer-overflow vulnerability because it fails to
perform boundary checks before copying user-supplied data to
insufficiently sized memory buffers. The issue affects the ‘mbstring’
extension included in the standard distribution.
An attacker can exploit this issue to execute arbitrary machine
code in the context of the affected webserver. Failed exploit attempts
will likely crash the webserver, denying service to legitimate
users.