A containerd security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, and 21.04.

==========================================================================
Ubuntu Security Notice USN-5100-1
October 04, 2021

containerd vulnerability
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

containerd would allow unintended access to files.

Software Description:
- containerd: daemon to control runC

Details:

It was discovered that containerd insufficiently restricted permissions on
container root and plugin directories. If a user or automated system were
tricked into launching a specially crafted container image, a remote
attacker could traverse directory contents and modify files and execute
programs on the host filesystem, possibly leading to privilege escalation.

Update instructions:

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

Ubuntu 21.04:
containerd 1.5.2-0ubuntu1~21.04.3

Ubuntu 20.04 LTS:
containerd 1.5.2-0ubuntu1~20.04.3

Ubuntu 18.04 LTS:
containerd 1.5.2-0ubuntu1~18.04.3

After a standard system update you need to restart containerd to make
all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-5100-1
CVE-2021-41103

Package Information:
  https://launchpad.net/ubuntu/+source/containerd/1.5.2-0ubuntu1~21.04.3
  https://launchpad.net/ubuntu/+source/containerd/1.5.2-0ubuntu1~20.04.3
  https://launchpad.net/ubuntu/+source/containerd/1.5.2-0ubuntu1~18.04.3