Ubuntu 20.04 LTS USN-4728-1 Moderate: Snapd Privilege Escalation Risk

ubuntu

February 10, 2021

An intended access restriction in snapd could be bypassed by container management snaps.

Summary

An intended access restriction in snapd could be bypassed by container

management snaps.

Software Description:

- snapd: Daemon and tooling that enable snap packages

Details:

Gilad Reti discovered that snapd did not correctly specify cgroup

delegation when generating systemd service units for various container

management snaps. This could allow a local attacker to escalate privileges

via access to arbitrary devices of the container host from within a

compromised or malicious container.

Topics Covered

security advisory moderate privilege escalation access control Ubuntu ubuntu escalation container container management snapd

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.10:
  snapd                           2.48.3+20.10

Ubuntu 20.04 LTS:
  snapd                           2.48.3+20.04

Ubuntu 18.04 LTS:
  snapd                           2.48.3+18.04

Ubuntu 16.04 LTS:
  snapd                           2.48.3

In general, a standard system update will make all the necessary changes.
On Ubuntu, snapd will automatically refresh itself to snapd 2.48.3 which is
unaffected. Affected container management snaps will also automatically
refresh which will restart containers and resolve this vulnerability.