A PySAML2 security update has been released for Ubuntu Linux 16.04 ESM.

USN-5066-2: PySAML2 vulnerability

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Ubuntu Security Notice USN-5066-2
September 08, 2021

python-pysaml2 vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 ESM

Summary:

PySAML2 could be made to accept invalid SAML documents.

Software Description:
- python-pysaml2: Pure python implementation of SAML2

Details:

USN-5066-1 fixed a vulnerability in PySAML2. This update provides
the corresponding update for Ubuntu 16.04 ESM.

Original advisory details:

Brian Wolff discovered that PySAML2 incorrectly validated cryptographic
signatures. A remote attacker could possibly use this issue to alter SAML
documents.

Update instructions:

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

Ubuntu 16.04 ESM:
python-pysaml2 3.0.0-3ubuntu1.16.04.4+esm1
python3-pysaml2 3.0.0-3ubuntu1.16.04.4+esm1

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

References:
  https://ubuntu.com/security/notices/USN-5066-2
  https://ubuntu.com/security/notices/USN-5066-1
CVE-2021-21239