This might be useful for you.
Code:
#!/bin/bash
# timthumb.php fix
# replace timthumb.php with fresh non vuln version
wget -q -O ~/newtim.php http://timthumb.googlecode.com/svn/trunk/timthumb.php
find . -name "timthumb.php" -exec bash -c "echo patching {} && cp ~/newtim.php {}" \;
rm ~/newtim.php
will replace all copies of timthumb.php on your server with a fresh copy from the trunk.