The remote host is missing an update to ntp announced via advisory DSA 1702-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201702-1

It has been discovered that NTP, an implementation of the Network Time Protocol, does not properly check the result of an OpenSSL function for verifying cryptographic signatures, which may ultimately lead to the acceptance of unauthenticated time information. (Note that cryptographic authentication of time servers is often not enabled in the first place.) For the stable distribution (etch), this problem has been fixed in version 4.2.2.p4+dfsg-2etch1. For the unstable distribution (sid), this problem has been fixed in version 4.2.4p4+dfsg-8. The testing distribution (lenny) will be fixed soon. We recommend that you upgrade your ntp package.