The remote host is missing an update to unbound announced via advisory DSA 2243-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202243-1

It was discovered that Unbound, a caching DNS resolver, ceases to provide answers for zones signed using DNSSEC after it has processed a crafted query. (CVE-2009-4008) In addition, this update improves the level of DNSSEC support in the lenny version of Unbound so that it is possible for system administrators to configure the trust anchor for the root zone. For the oldstable distribution (lenny), this problem has been fixed in version 1.4.6-1~lenny1. For the other distributions (squeeze, wheezy, sid), this problem has been fixed in version 1.4.4-1. We recommend that you upgrade your unbound packages.