Can not use session out slide application folder in CI 3.0

I have problem with CI 3.0 to use session outside application folder for Ckfinder and set authentication below but show error disable security reasons.


$sess = unserialize($_COOKIE['ci_session']);

if($sess['sess_xxxxxxx']!="xxxxx"){
return false;
}else{
return true;
}

I've tried with CI 3.0 Dev it working good. Thank you for answer in advance.