Sudo: must be setuid root

Here is a solution to a common error when using sudo

Open terminal (CTRL+ALT+T) and use below commands

loginuser> sudo -l
sudo: must be setuid root
loginuser>

To fix the error above chown and chmod the sudo file as root, in my case the file is in /usr/bin

root>chown root:root /usr/bin/sudo
root>chmod 4755 /usr/bin/sudo
root>chmod 0400 /etc/sudoers
reboot system

That should fix the error and you should be able to sudo without a problem.

Note: You must be login with "root" user.