The PAM conversation function in OpenSSH 3.7.1 and 3.7.1p1 interprets an array of structures as an array of pointers, which allows attackers to modify the stack and possibly gain privileges.
http://www.securityfocus.com/bid/8677
http://www.securityfocus.com/archive/1/338617
http://www.securityfocus.com/archive/1/338616
http://www.openssh.com/txt/sshpam.adv
http://www.kb.cert.org/vuls/id/209807
http://lists.grok.org.uk/pipermail/full-disclosure/2003-September/010812.html