The PPP daemon (pppd) in Apple Mac OS X 10.4.8 checks ownership of the stdin file descriptor to determine if the invoker has sufficient privileges, which allows local users to load arbitrary plugins and gain root privileges by bypassing this check.
https://exchange.xforce.ibmcloud.com/vulnerabilities/34503
http://www.vupen.com/english/advisories/2007/1939
http://www.securitytracker.com/id?1018124
http://www.securityfocus.com/bid/24144
http://secunia.com/advisories/25402
http://lists.apple.com/archives/security-announce/2007/May/msg00004.html
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=537