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[USN-7955-1] urllib3 vulnerability

Posted on 12 January 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-7955-1
January 12, 2026

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

- Ubuntu 25.10
- Ubuntu 25.04
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

urllib3 could be made to use excessive resources if it received specially
crafted network traffic.

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

Details:

It was discovered that urllib3 incorrectly handled decompression during
HTTP redirects. An attacker could possibly use this issue to cause urllib3
to use excessive resources, causing a denial of service.

Update instructions:

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

Ubuntu 25.10
python3-urllib3 2.3.0-3ubuntu0.2

Ubuntu 25.04
python3-urllib3 2.3.0-2ubuntu0.3

Ubuntu 24.04 LTS
python3-urllib3 2.0.7-1ubuntu0.4

Ubuntu 22.04 LTS
python3-urllib3 1.26.5-1~exp1ubuntu0.5

Ubuntu 20.04 LTS
python3-urllib3 1.25.8-2ubuntu0.4+esm3
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-7955-1
CVE-2026-21441

Package Information:
https://launchpad.net/ubuntu/+source/python-urllib3/2.3.0-3ubuntu0.2
https://launchpad.net/ubuntu/+source/python-urllib3/2.3.0-2ubuntu0.3
https://launchpad.net/ubuntu/+source/python-urllib3/2.0.7-1ubuntu0.4
https://launchpad.net/ubuntu/+source/python-urllib3/1.26.5-1~exp1ubuntu0.5

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