It is possible to bypass the open_basedir restriction in PHP 4.4.2 and 5.1.2 by using the tempnam() function.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/45438/open_basedir-bypass.txt
Source: https://packetstormsecurity.com/files/45438/open_basedir-bypass.txt.html