fetchmail email client before 5.9.10 does not properly limit the maximum number of messages available, which allows a remote IMAP server to overwrite memory via a message count that exceeds the boundaries of an array.
http://www.securityfocus.com/bid/4788
http://www.redhat.com/support/errata/RHSA-2002-047.html
http://www.linux-mandrake.com/en/security/2002/MDKSA-2002-036.php