The remote host is missing an update to unbound announced via advisory DSA 2370-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202370-1

It was discovered that Unbound, a recursive DNS resolver, would crash when processing certain malformed DNS responses from authoritative DNS servers, leading to denial of service. CVE-2011-4528 Unbound attempts to free unallocated memory during processing of duplicate CNAME records in a signed zone. CVE-2011-4869 Unbound does not properly process malformed responses which lack expected NSEC3 records. For the oldstable distribution (lenny), these problems have been fixed in version 1.4.6-1~lenny2. For the stable distribution (squeeze), these problems have been fixed in version 1.4.6-1+squeeze2. For the testing distribution (wheezy) and the unstable distribution (sid), these problems have been fixed in version 1.4.14-1. We recommend that you upgrade your unbound packages.