Uninstalling default VBoxGuestAdditions on Debian

It's hard to tell what is going on if you can't remember or do not know where your old install of guest additions came from.

Do you have virtualbox-guest-additions installed? You can uninstall it by running (as a superuser)

apt-get remove virtualbox-guest-additions

If that's not it, I would recommend trying to follow the instructions at the VirtualBox website. Since it appears you already have an old version of the guest additions installed, try the uninstallation instructions:

sh ./VBoxLinuxAdditions.run uninstall

Here's how I did it just now, after everything above failed...

sudo bash /opt/VBoxGuestAdditions-*/uninstall.sh

This worked for me -

sudo apt-get purge virtualbox*

Source: https://forums.virtualbox.org/viewtopic.php?f=7&t=65539

And this explains the problem -

Note that some Linux distributions already come with all or part of the VirtualBox Guest Additions. You may choose to keep the distribution's version of the Guest Additions but these are often not up to date and limited in functionality, so we recommend replacing them with the Guest Additions that come with VirtualBox. The VirtualBox Linux Guest Additions installer tries to detect existing installation and replace them but depending on how the distribution integrates the Guest Additions, this may require some manual interaction. It is highly recommended to take a snapshot of the virtual machine before replacing pre-installed Guest Additions.

https://www.virtualbox.org/manual/ch04.html