OpenSSH 4.0, and other versions before 4.2, does not properly handle dynamic port forwarding ("-D" option) when a listen address is not provided, which may cause OpenSSH to enable the GatewayPorts functionality.
http://marc.info/?l=bugtraq&m=112605977304049&w=2
http://secunia.com/advisories/16686
http://secunia.com/advisories/18010
http://secunia.com/advisories/18661
http://secunia.com/advisories/19243
http://securitytracker.com/id?1014845
http://support.avaya.com/elmodocs2/security/ASA-2006-033.htm