A python-apt regression update has been released for Ubuntu 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

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Ubuntu Security Notice USN-4668-3
January 04, 2021

python-apt regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

USN-4668-1 introduced a regression in python-apt.

Software Description:
- python-apt: Python interface to libapt-pkg

Details:

USN-4668-1 fixed vulnerabilities in python-apt. The update caused a
regression when using certain APIs with a file handle. This update fixes
the problem.

We apologize for the inconvenience.

Original advisory details:

Kevin Backhouse discovered that python-apt incorrectly handled resources. A
local attacker could possibly use this issue to cause python-apt to consume
resources, leading to a denial of service.

Update instructions:

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

Ubuntu 20.10:
python3-apt 2.1.3ubuntu1.3

Ubuntu 20.04 LTS:
python-apt 2.0.0ubuntu0.20.04.3
python3-apt 2.0.0ubuntu0.20.04.3

Ubuntu 18.04 LTS:
python-apt 1.6.5ubuntu0.5
python3-apt 1.6.5ubuntu0.5

Ubuntu 16.04 LTS:
python-apt 1.1.0~beta1ubuntu0.16.04.11
python3-apt 1.1.0~beta1ubuntu0.16.04.11

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

References:
  https://usn.ubuntu.com/4668-3
  https://usn.ubuntu.com/4668-1
  https://launchpad.net/bugs/1907676

Package Information:
  https://launchpad.net/ubuntu/+source/python-apt/2.1.3ubuntu1.3
  https://launchpad.net/ubuntu/+source/python-apt/2.0.0ubuntu0.20.04.3
  https://launchpad.net/ubuntu/+source/python-apt/1.6.5ubuntu0.5
  https://launchpad.net/ubuntu/+source/python-apt/1.1.0~beta1ubuntu0.16.04.11