Comment 46 for bug 1565985

I can confirm, this is broken in v20160822.0.0. I tried rolling back to v20160805.0.0, but that also seems to fail.

ubuntu@ubuntu-xenial:~$ modinfo vboxguest
filename: /lib/modules/4.4.0-34-generic/kernel/ubuntu/vbox/vboxguest/vboxguest.ko
version: 5.0.18_Ubuntu
license: GPL
description: Oracle VM VirtualBox Guest Additions for Linux Module
author: Oracle Corporation
srcversion: A2B0E3228AD033CF730FD74
alias: pci:v000080EEd0000CAFEsv00000000sd00000000bc*sc*i*
depends:
intree: Y
vermagic: 4.4.0-34-generic SMP mod_unload modversions

I'm currently on VirtualBox Version 5.1.4 r110228. I'm able to fix this by downloading v5.1.4 guest additions from here: http://download.virtualbox.org/virtualbox/5.1.4/

Note, you'll need to install the following packages in order to compile the guest additions:
* gcc
* build-essentials
* linuz-headers-$(uname-a) // your architecture here