The remote host is missing an update to netkit-rwho announced via advisory DSA 678-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20678-1

Vlad902 discovered a vulnerability in the rwhod program that can be used to crash the listening process. The broadcasting one is unaffected. This vulnerability only affects little endian architectures (i.e. on Debian: alpha, arm, alpha, ia64, i386, mipsel and s390). For the stable distribution (woody) this problem has been fixed in version 0.17-4woody2. For the unstable distribution (sid) this problem has been fixed in version 0.17-8. We recommend that you upgrade your rwhod package.