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Ubuntu Security Notice USN-5103-1
October 04, 2021

docker.io vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM

Summary:

Docker could be made to adjust the permissions of files.

Software Description:
- docker.io: Linux container runtime

Details:

Lei Wang and Ruizhi Xiao discovered that the Moby Docker engine in
Docker incorrectly allowed the docker cp command to make permissions
changes in the host filesystem in some situations. A local attacker
could possibly use to this to expose sensitive information or gain
administrative privileges.

Update instructions:

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

Ubuntu 21.04:
  docker.io                       20.10.7-0ubuntu1~21.04.2

Ubuntu 20.04 LTS:
  docker.io                       20.10.7-0ubuntu1~20.04.2

Ubuntu 18.04 LTS:
  docker.io                       20.10.7-0ubuntu1~18.04.2

Ubuntu 16.04 ESM:
  docker.io                       18.09.7-0ubuntu1~16.04.9+esm1

In general, a standard system update will make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-5103-1
  CVE-2021-41089

Package Information:
  https://launchpad.net/ubuntu/+source/docker.io/20.10.7-0ubuntu1~21.04.2
  https://launchpad.net/ubuntu/+source/docker.io/20.10.7-0ubuntu1~20.04.2
  https://launchpad.net/ubuntu/+source/docker.io/20.10.7-0ubuntu1~18.04.2