The remote host is vulnerable to a remote 'format string' flaw.
The remote host is running a version of PHP that is older than 5.1.2. Versions 5.1.0 and 5.1.1 are potentially vulnerable to a remote format string vulnerabilty. Specifically, if PHP is configured to log MySQL errors, then an attacker may be able to trigger a condition wherein arbitrary commands or code are executed.
Upgrade to version 5.1.2 or higher.