The default configuration of OpenSSH through 6.1 enforces a fixed time limit between establishing a TCP connection and completing a login, which makes it easier for remote attackers to cause a denial of service (connection-slot exhaustion) by periodically making many new TCP connections.
marc.info/?l=bugtraq&m=144050155601375&w=2
rhn.redhat.com/errata/RHSA-2013-1591.html
www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/servconf.c?r1=1.234#rev1.234
www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshd_config.5?r1=1.156#rev1.156
www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshd_config?r1=1.89#rev1.89
www.openwall.com/lists/oss-security/2013/02/07/3
www.oracle.com/technetwork/topics/security/cpujan2015-1972971.html
www.oracle.com/technetwork/topics/security/linuxbulletinjan2016-2867209.html
www.securityfocus.com/bid/58162
bugzilla.redhat.com/show_bug.cgi?id=908707
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A19515
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A19595