An authentication bypass vulnerability in the polkit auth system service, which is installed by default on many recent Linux distributions, allows unprivileged attackers to gain a root shell. On June 3, 2021, the polkit local privilege escalation flaw (CVE-2021-3560) was officially identified, and a fix was released. Polkit is used by systemd, hence it’s included in any Linux distribution that uses systemd.
Kevin Backhouse, a GitHub security researcher, detailed how he discovered the bug (CVE-2021-3560) in a systemd service called polkit in a blog post on Thursday. The problem, which was first introduced in commit bfa5036 seven years ago and first shipped in polkit version 0.113, took various pathways in different Linux distributions. Despite the fact that many Linux distributions did not ship with the vulnerable polkit version until recently, any Linux machine with polkit 0.113 or later installed is vulnerable to attacks.