CakePHP how to share session with Vbulletin

how to put folder of vbulletin and modify .htaccess file in cake PHP in purpose use them in same session ? if it possible, plz help me by post the way to put the folder vbulletin in order request access from localhost/forum or localhost/app_name/forum?

I am tried to install vbullentin in webroot and modify .htaccess. It can access from localhost/forum ( app cake can access from http://localhost ) but both couldnt share session .