functions/imap_general.php in SquirrelMail, as used in Red Hat Enterprise Linux (RHEL) 4 and 5, does not properly handle 8-bit characters in passwords, which allows remote attackers to cause a denial of service (disk consumption) by making many IMAP login attempts with different usernames, leading to the creation of many preference files. NOTE: this issue exists because of an incorrect fix for CVE-2010-2813.
https://bugzilla.redhat.com/show_bug.cgi?id=814671
http://www.openwall.com/lists/oss-security/2012/04/20/22