How to upgrade to VirtualBox Guest Additions on VM box?

I've got the latest version of VirtualBox installed on my desktop (4.3.4). I'm using Vagrant to run a VM based on the example 64-bit Ubuntu 12.04 LTS box at: http://files.vagrantup.com/precise64.box Everytime I run `vagrant up`, I get the following warning: The guest additions on this VM do not match the installed version of VirtualBox! In most cases this is fine, but in rare cases it can cause things such as shared folders to not work properly. If you see shared folder errors, please update the guest additions within the virtual machine and reload your VM. Guest Additions Version: 4.2.0 VirtualBox Version: 4.3 I've googled, but I can't find a way to upgrade to Guest Additions v4.3. The latest version in the Ubuntu repository for precise is 4.1, and there's no download link on the official VirtualBox download page.