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[USN-8811-1] urllib3 vulnerability

Posted on 24 September 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8811-1
September 24, 2026

python-urllib3 vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

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

Summary:

urllib3 could be made to expose sensitive information over the network.

Software Description:
- python-urllib3: HTTP library with thread-safe connection pooling

Details:

It was discovered that urllib3 did not correctly strip sensitive HTTP
headers during cross-origin redirects. An attacker could possibly use this
issue to leak sensitive information.

Update instructions:

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

Ubuntu 20.04 LTS
python3-urllib3 1.25.8-2ubuntu0.4+esm5
Available with Ubuntu Pro

Ubuntu 18.04 LTS
python-urllib3 1.22-1ubuntu0.18.04.2+esm4
Available with Ubuntu Pro
python3-urllib3 1.22-1ubuntu0.18.04.2+esm4
Available with Ubuntu Pro

Ubuntu 16.04 LTS
python-urllib3 1.13.1-2ubuntu0.16.04.4+esm4
Available with Ubuntu Pro
python3-urllib3 1.13.1-2ubuntu0.16.04.4+esm4
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8811-1
CVE-2026-44431

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