The remote host is missing an update to krb4 announced via advisory DSA 273-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20273-1

A cryptographic weakness in version 4 of the Kerberos protocol allows an attacker to use a chosen-plaintext attack to impersonate any principal in a realm. Additional cryptographic weaknesses in the krb4 implementation permit the use of cut-and-paste attacks to fabricate krb4 tickets for unauthorized client principals if triple-DES keys are used to key krb4 services. These attacks can subvert a site's entire Kerberos authentication infrastructure. For the stable distribution (woody) this problem has been fixed in version 1.1-8-2.3. For the old stable distribution (woody) this problem has been fixed in version 1.0-2.3. For the unstable distribution (sid) this problem has been fixed in version 1.2.2-1. We recommend that you upgrade your krb4 packages immediately.