The remote host is missing an update to l2tpd announced via advisory DSA 152-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20152-1

Current versions of l2tpd, a layer 2 tunneling client/server program, forgot to initialize the random generator which made it vulnerable since all generated random number were 100% guessable. When dealing with the size of the value in an attribute value pair, too many bytes were able to be copied, which could lead into the vendor field being overwritten. These problems have been fixed in version 0.67-1.1 for the current stable distribution (woody) and in version 0.68-1 for the unstable distribution (sid). The old stable distribution (potato) is not affected, since it doesn't contain the l2tpd package. We recommend that you upgrade your l2tpd packages.