USN-6851-2: Netplan regression

USN-6851-1 fixed vulnerabilities in Netplan. The update lead to the discovery of
a regression in netplan which caused systemctl enable to fail on systems where
systemd is not running. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Andreas Hasenack discovered that netplan incorrectly handled the permissions
for netdev files containing wireguard configuration. An attacker could use
this to obtain wireguard secret keys.

It was discovered that netplan configuration could be manipulated into injecting
arbitrary commands …

advisory configuration discovery enable fail files fixes permissions problem running systemd systems update usn vulnerabilities wireguard