Errors with /etc/sudoers with Ubuntu

Hello
I having issues with sudo -s command
i am having this errors

ansible@ansible-new:~$ sudo -s
sudo: /etc/sudoers is world writable
sudo: no valid sudoers sources found, quitting...
sudo: unable to initialise policy plug-in
ansible@ansible-new:~$

I have tried to go into single mode to remount /
but I cannot perform this action as it is a virtual box with ubuntu 16.04 and the keyboards cannot accept some characters
I also dont have the root password to perform
a pkexec visudo command

Not sure why a virtual box environment or keyboard incompatibilities should influence this. The error and its remedy are quite clear. man sudoers :