The document in this archive illustrates using the included proof of concept exploit to achieve root on Ubuntu systems using a flaw in the OverlayFS file system. The exploit itself does not have author attribution as the proof of concept came through SSD Disclosures.
You can download it from the following link: https://packetstormsecurity.com/files/download/162866/CVE-2021-3493.tgz
Source: https://packetstormsecurity.com/files/162866/Ubuntu-OverlayFS-Local-Privilege-Escalation.html