Description:
Mambo is a popular Open Source Content Management System released under the GNU General Public license (GNU GPL). There
are unfortunately some serious flaws in Mambo's login feature that allow for authentication bypass. This can be used to
access arbitrary accounts, but even worse can be used to eventually install harmful modules and execute arbitrary php code
on the server running Mambo. The Mambo team have committed fixes for these issues to SVN, and patches are available from the
official Mambo website. Users are encouraged to patch the vulnerable functionality or update their Mambo installation as soon
as possible.
Authentication Bypass
Mambo is vulnerable to an Authentication Bypass issue that is due to an SQL Injection in the login function. The SQL Injection
is possible because the $passwd variable is only sanitized when it is not passed as an argument to the function.
function login( $username=null,$passwd=null ) {
global $acl;
$usercookie = mosGetParam( $_COOKIE, 'usercookie', '' );
$sessioncookie = mosGetParam( $_COOKIE, 'sessioncookie', '' );
if (!$username || !$passwd) {
$username = trim( mosGetParam( $_POST, 'username', '' ) );
$passwd = trim( mosGetParam( $_POST, 'passwd', '' ) );
$passwd = md5( $passwd );
$bypost = 1;
}
$remember = trim( mosGetParam( $_POST, 'remember', '' ) );
if (!$username || !$passwd) {
echo "<script> alert(\""._LOGIN_INCOMPLETE."\"); window.history.go(-1); </script>\n";
exit();
} else {
$username = $this->_db->getEscaped($username);
$this->_db->setQuery( "SELECT id, gid, block, usertype"
. "\nFROM #__users"
. "\nWHERE username='$username' AND password='$passwd'"
);
As seen in the above code it is assumed that the $passwd variable is an md5 hash, but when sending a cookie with values like
"usercookie[password]=%27 or 1=1/*; usercookie[username]=admin" the query is broken, and the password is never checked correctly.
This issue would probably be limited to SQL Injection, but Mambo allows a user to change their password without knowing the original
password. They just have to be logged in to the particular account that they want to change the password for. Using this strategy
an attacker could login as the admin using the authentication bypass vulnerability, change the admin password, and then successfully log
into the admin section where uploading arbitrary php code via the "install module" function.
Solution:
The Mambo development team have committed updates to SVN, and the patches can be obtained by visiting the official mambo website.
Credits:
James Bercegay of the GulfTech Security Research Team
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