The remote web server uses a version of PHP that is affected by multiple buffer overflows.
According to its banner, the version of PHP installed on the remote host is older than 5.2.0. Such versions may be affected by several buffer overflows. To exploit these issues, an attacker would need the ability to upload an arbitrary PHP script to the remote server, or to be able to manipulate several variables processed by some PHP functions such as htmlentities().
Upgrade to version 5.2.0 or higher.