Juniper ScreenOS before 6.3.0r21, when ssh-pka is configured and enabled, allows remote attackers to cause a denial of service (system crash) or execute arbitrary code via crafted SSH negotiation.
http://www.securitytracker.com/id/1034490
http://www.securityfocus.com/bid/79627
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10712