[USN-7955-2] urllib3 regression

[noreply+usn-bot at canonical.com]

==========================================================================
Ubuntu Security Notice USN-7955-2
January 19, 2026

python-urllib3 regression
==========================================================================

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

- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

USN-7955-1 introduced a regression in urllib3

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

Details:

USN-7955-1 fixed vulnerabilities in urllib3. The update introduced a
regression in response streaming on Ubuntu 20.04 LTS and Ubuntu 22.04 LTS.
This update fixes the problem.

We apologize for the inconvenience.

Original advisory 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 22.04 LTS
  python3-urllib3                 1.26.5-1~exp1ubuntu0.6

Ubuntu 20.04 LTS
  python3-urllib3                 1.25.8-2ubuntu0.4+esm4
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-7955-2
  https://ubuntu.com/security/notices/USN-7955-1
  CVE-2026-21441, https://bugs.launchpad.net/bugs/2138420

Package Information:
  https://launchpad.net/ubuntu/+source/python-urllib3/1.26.5-1~exp1ubuntu0.6
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