The remote host is missing an update to ldns announced via advisory DSA 1795-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201795-1

Stefan Kaltenbrunner discovered that ldns, a library and set of utilities to facilitate DNS programming, did not correctly implement a buffer boundary check in its RR DNS record parser. This weakness could enable overflow of a heap buffer if a maliciously-crafted record is parsed, potentially allowing the execution of arbitrary code. The scope of compromise will vary with the context in which ldns is used, and could present either a local or remote attack vector. The old stable distribution (etch) is not affected by this issue. For the stable distribution (lenny), this problem has been fixed in version 1.4.0-1+lenny1. For the unstable distribution (sid), this problem was fixed in version 1.5.1-1. We recommend that you upgrade your ldns packages.