Format string vulnerability in flog function of eXtremail 1.1.9 and earlier allows remote attackers to gain root privileges via format specifiers in the SMTP commands (1) HELO, (2) EHLO, (3) MAIL FROM, or (4) RCPT TO, and the POP3 commands (5) USER and (6) other commands that can be executed after POP3 authentication.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6733
http://www.extremail.com/news.htm
http://www.extremail.com/history.htm
http://archives.neohapsis.com/archives/bugtraq/2001-06/0291.html