I found a very old bugreport on debian about the same type of error which doesn't seem to have been fixed .
It might be triggered by wrong permissions. The right permissions would be 0440
That old bug seems also to be triggered easily by, for instance, a wrong character in one of the lines in /etc/sudoers
I don't think it's unthinkable that it could be triggered by VMS/Windows line endings (CR-LF).
OTOH. I might be completely wrong about this.
@pavlos_kairis , what do you think ? Could it be possible ?
I think it is pretty scary if a simple mistake in a configfile could trigger this kind of error.