/usr/src/linux-headers-4.13.0-36-generic/certs is in linux-headers-4.13.0-36-generic 4.13.0-36.40~16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/src/linux-headers-4.13.0-36-generic/../linux-headers-4.13.0-36/certs