Off-by-one error in Pegasus Mail 4.21a through 4.21c and 4.30PB1 allows remote attackers to execute arbitrary code via a long email message header, which triggers a one-byte buffer overflow.
http://www.securityfocus.com/bid/15973
http://www.securityfocus.com/archive/1/419908/100/0/threaded
http://www.pmail.com/newsflash.htm#secunia
http://securitytracker.com/id?1015385