Getting trouble with Sudo permissions

[dmahesh22]

When I've give "sudo bash" in terminal, following error message is displaying

sudo : /etc/sudoers is mode 0555, should be 0440
sudo : no valid sudoers sources found,quitting
sudo : unable to initialize policy plugin

What might be wrong, suddenly this message was showing.

[pkadeel]

When I've give "sudo bash" in terminal, following error message is displaying

sudo : /etc/sudoers is mode 0555, should be 0440
sudo : no valid sudoers sources found,quitting
sudo : unable to initialize policy plugin

What might be wrong, suddenly this message was showing.

/etc/sudoers is by default 0440. you might have changed that accidentally
can you run other sudo commands? if yes then revert it back to 0440

sudo chmod 0440 /etc/sudoers

[dmahesh22]

the above command is not working,because actual trouble with "Sudo".

Thanks for reply

[steeldriver]

I think you will need to boot into the recovery console, remount the root filesystem read-write, and do the chmod from there

# mount -o remount,rw /
# chmod 0440 /etc/sudoers
# exit

If you changed file modes on other stuff that you shouldn't (e.g. by doing a recursive chmod in the root filesystem) then other things may be broken as well though.