The remote host is missing an update to bind9 announced via advisory DSA 2517-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202517-1

Einar Lonn discovered that under certain conditions bind9, a DNS server, may use cached data before initialization. As a result, an attacker can trigger and assertion failure on servers under high query load that do DNSSEC validation. For the stable distribution (squeeze), this problem has been fixed in version 1:9.7.3.dfsg-1~squeeze6. For the testing distribution (wheezy), this problem will be fixed soon. For the unstable distribution (sid), this problem has been fixed in version 1:9.8.1.dfsg.P1-4.2. We recommend that you upgrade your bind9 packages.