==========================================================================
Ubuntu Security Notice USN-7927-1
December 11, 2025

python-urllib3 vulnerabilities
==========================================================================

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:

Several security issues were fixed in urllib3.

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

Details:

Illia Volochii discovered that urllib3 did not limit the steps in a
decompression chain. An attacker could possibly use this issue to cause
urllib3 to use excessive resources, causing a denial of service.
(CVE-2025-66418)

Rui Xi discovered that urllib3 incorrectly handled highly compressed data.
An attacker could possibly use this issue to cause urllib3 to use excessive
resources, causing a denial of service. This issue only affected Ubuntu
24.04 LTS, Ubuntu 25.04, and Ubuntu 25.10. (CVE-2025-66471)

For the brotli encoding, the fix for CVE-2025-66471 requires an additional
security update in the brotli package.

Update instructions:

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

Ubuntu 25.10
  python3-urllib3                 2.3.0-3ubuntu0.1

Ubuntu 25.04
  python3-urllib3                 2.3.0-2ubuntu0.2

Ubuntu 24.04 LTS
  python3-urllib3                 2.0.7-1ubuntu0.3

Ubuntu 22.04 LTS
  python3-urllib3                 1.26.5-1~exp1ubuntu0.4

Ubuntu 20.04 LTS
  python3-urllib3                 1.25.8-2ubuntu0.4+esm2
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-7927-1
  CVE-2025-66418, CVE-2025-66471

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