A vulnerable version of FreeSSHd is installed on the remote host. Description : The version installed does not validate key exchange strings send by a SSH client. This results in a buffer overflow and possible a compromise of the host if the client is sending a long key exchange string.
Upgrade to the latest release. See second url in the 'See also' section. Note : At this point the FreeSSHD Service is reported down. You should start it manualy again.