openwebmail_init in Open WebMail 1.81 and earlier allows local users to execute arbitrary code via .. (dot dot) sequences in a login name, such as the name provided in the sessionid parameter for openwebmail-abook.pl, which is used to find a configuration file that specifies additional code to be executed.
https://exchange.xforce.ibmcloud.com/vulnerabilities/10904
http://www.securityfocus.com/bid/6425
http://sourceforge.net/forum/forum.php?thread_id=782605&forum_id=108435