An issue was discovered in libraries/common.inc.php in phpMyAdmin 4.0 before 4.0.10.20, 4.4.x, 4.6.x, and 4.7.0 prereleases. The restrictions caused by $cfg["Servers"][$i]["AllowNoPassword"] = false are bypassed under certain PHP versions . This can allow the login of users who have no password set even if the administrator has set $cfg["Servers"][$i]["AllowNoPassword"] to false . This occurs because some implementations of the PHP substr function return false when given "" as the first argument.