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.