Provide references for CVE-2018-18556.
Where can I find more information about CVE-2018-18556?
References are available at: https://blog.vyos.io/the-operator-level-is-proved-insecure-and-will-be-removed-in-the-next-releases, https://blog.mirch.io/2018/11/05/cve-2018-18556-vyos-privilege-escalation-via-sudo-pppd-for-operator-users/, http://packetstormsecurity.com/files/159234/VyOS-restricted-shell-Escape-Privilege-Escalation.html.