The remote host is missing an update to libxml2 announced via advisory DSA 2255-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202255-1

Chris Evans discovered that libxml was vulnerable to buffer overflows, which allowed a crafted XML input file to potentially execute arbitrary code. For the oldstable distribution (lenny), this problem has been fixed in version 2.6.32.dfsg-5+lenny4. For the stable distribution (squeeze), this problem has been fixed in version 2.7.8.dfsg-2+squeeze1. For the unstable distribution (sid), this problem has been fixed in version 2.7.8.dfsg-3. We recommend that you upgrade your libxml2 packages.