A PyYAML security update has been released for Ubuntu 20.04 LTS and 20.10.

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Ubuntu Security Notice USN-4940-1
May 10, 2021

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

- Ubuntu 20.10
- Ubuntu 20.04 LTS

Summary:

PyYAML could be made to run programs if it opened a specially crafted YAML
file.

Software Description:
- pyyaml: YAML parser and emitter for Python

Details:

It was discovered that PyYAML incorrectly handled untrusted YAML files with
the FullLoader loader. A remote attacker could possibly use this issue to
execute arbitrary code.

Update instructions:

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

Ubuntu 20.10:
python3-yaml 5.3.1-2ubuntu0.1

Ubuntu 20.04 LTS:
python-yaml 5.3.1-1ubuntu0.1
python3-yaml 5.3.1-1ubuntu0.1

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

References:
  https://ubuntu.com/security/notices/USN-4940-1
CVE-2020-14343

Package Information:
  https://launchpad.net/ubuntu/+source/pyyaml/5.3.1-2ubuntu0.1
  https://launchpad.net/ubuntu/+source/pyyaml/5.3.1-1ubuntu0.1