The remote host is missing an update to libxml2 announced via advisory DSA 2394-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202394-1

Many security problems had been fixed in libxml2, a popular library to handle XML data files. CVE-2011-3919: Jüri Aedla discovered a heap-based buffer overflow that allows remote attackers to cause a denial of service or possibly have unspecified other impact via unknown vectors. CVE-2011-0216: An Off-by-one error have been discoveried that allows remote attackers to execute arbitrary code or cause a denial of service. CVE-2011-2821: A memory corruption (double free) bug has been identified in libxml2's XPath engine. Through it, it is possible to an attacker allows cause a denial of service or possibly have unspecified other impact. This vulnerability does not affect the oldstable distribution (lenny). CVE-2011-2834: Yang Dingning discovered a double free vulnerability related to XPath handling. CVE-2011-3905: An out-of-bounds read vulnerability had been discovered, which allows remote attackers to cause a denial of service. For the oldstable distribution (lenny), this problem has been fixed in version 2.6.32.dfsg-5+lenny5. For the stable distribution (squeeze), this problem has been fixed in version 2.7.8.dfsg-2+squeeze2. For the testing distribution (wheezy), this problem has been fixed in version 2.7.8.dfsg-7. For the unstable distribution (sid), this problem has been fixed in version 2.7.8.dfsg-7. We recommend that you upgrade your libxml2 packages.