OpenSSH LoginGraceTime / MaxStartups DoS
Medium Nessus Plugin ID 67140
SynopsisThe remote SSH service is susceptible to a remote denial of service attack.
DescriptionAccording to its banner, a version of OpenSSH earlier than version 6.2 is listening on this port. The default configuration of OpenSSH installs before 6.2 could allow a remote attacker to bypass the LoginGraceTime and MaxStartups thresholds by periodically making a large number of new TCP connections and thereby prevent legitimate users from gaining access to the service.
Note that this plugin has not tried to exploit the issue or detect whether the remote service uses a vulnerable configuration. Instead, it has simply checked the version of OpenSSH running on the remote host.
SolutionUpgrade to OpenSSH 6.2 and review the associated server configuration settings.