packet.c in ssh in OpenSSH allows remote attackers to cause a denial of service (crash) by sending an invalid protocol sequence with USERAUTH_SUCCESS before NEWKEYS, which causes newkeys[mode] to be NULL.
http://bugs.gentoo.org/show_bug.cgi?id=148228
http://secunia.com/advisories/22245
http://secunia.com/advisories/22298
http://secunia.com/advisories/22495
http://secunia.com/advisories/23038
https://issues.rpath.com/browse/RPL-661
https://issues.rpath.com/browse/RPL-681
http://www.mandriva.com/security/advisories?name=MDKSA-2006:179
http://www.novell.com/linux/security/advisories/2006_24_sr.html
http://www.novell.com/linux/security/advisories/2006_62_openssh.html