The file "chap-secrets" is having read privileges for group and other/world. Need to remove the permissions.
vyos@vyos# ls -al /etc/ppp/ total 31 drwxr-xr-x 8 root root 306 Sep 27 10:03 . drwxr-xr-x 1 root root 4096 Dec 3 11:59 .. -rw-r--r-- 1 root root 78 Mar 8 2020 chap-secrets vyos@vyos# run sh ver Version: VyOS 1.2.5 Built by: Sentrium S.L.