Directory traversal vulnerability in the setuid root helper binary in S-nail (later S-mailx) before 14.8.16 allows local users to write to arbitrary files and consequently gain root privileges via a .. (dot dot) in the randstr argument.
https://www.mail-archive.com/s-nail-users%40lists.sourceforge.net/msg00551.html
http://www.securityfocus.com/bid/96138