The remote Debian host is missing a security-related update.
It was discovered that PHP could perform an invalid free request when processing crafted XML documents, corrupting the heap and potentially leading to arbitrary code execution. Depending on the PHP application, this vulnerability could be exploited remotely.
Upgrade the php5 packages. For the oldstable distribution (squeeze), this problem has been fixed in version 5.3.3-7+squeeze16. For the stable distribution (wheezy), this problem has been fixed in version 5.4.4-14+deb7u3.