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[USN-8104-1] Flask vulnerability

Posted on 18 March 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8104-1
March 18, 2026

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

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

Flask could be made to expose sensitive information over the
network.

Software Description:
- flask: Micro web framework based on Werkzeug and Jinja2

Details:

Shourya Jaiswal discovered that Flask did not correctly mark certain web
responses as user-specific. A remote attacker could possibly use this
issue to obtain sensitive information.

Update instructions:

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

Ubuntu 24.04 LTS
python3-flask 3.0.2-1ubuntu1.1

Ubuntu 22.04 LTS
python3-flask 2.0.1-2ubuntu1.2

Ubuntu 20.04 LTS
python3-flask 1.1.1-2ubuntu0.1+esm1
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8104-1
CVE-2026-27205

Package Information:
https://launchpad.net/ubuntu/+source/flask/3.0.2-1ubuntu1.1
https://launchpad.net/ubuntu/+source/flask/2.0.1-2ubuntu1.2

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