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Fedora 43 python-urllib3 Important DoS Threat Fix 2025-66418

fedora
Calendar Grey December 12, 2025
Dist Fedora Esm H88
Fix for Important DoS threat in Python-urllib3 on Fedora 43 addresses excessive resource consumption and enhances security.
Update brotli to 1.2.0 and python-urllib3 to 2.6.1

Summary

urllib3 is a powerful, user-friendly HTTP client for Python. urllib3 brings

many critical features that are missing from the Python standard libraries:

\u2022 Thread safety.

\u2022 Connection pooling.

\u2022 Client-side SSL/TLS verification.

\u2022 File uploads with multipart encoding.

\u2022 Helpers for retrying requests and dealing with HTTP redirects.

\u2022 Support for gzip, deflate, brotli, and zstd encoding.

\u2022 Proxy support for HTTP and SOCKS.

\u2022 100% test coverage.

Update Information:

Update brotli to 1.2.0 and python-urllib3 to 2.6.1. In python-urllib3: Fixed a security issue where streaming API could improperly handle highly compressed HTTP content ("decompression bombs") leading to excessive resource consumption even when a small amount of data was requested. Reading small chunks of compressed data is safer and much more efficient now. (CVE-2025-66471 / `GHSA-2xpw-w6gg-jr37) Fixed a security issue where an attacker could compose an HTTP response with virtually unlimited links in the Content-Encoding header, potentially leading to a denial of service (DoS) attack by exhausting system resources during decoding. The number of allowed chained encodings is now limited to 5. (CVE-2025-66418 / `GHSA-gm62-xv2j-4w53)

Topics%20covered

Topics Covered

security advisory denial of service fedora important python-urllib3 streaming api

Change Log

* Mon Dec 8 2025 Benjamin A. Beasley - 2.6.1-1 - Update to 2.6.1 (close RHBZ#2419408) - Fixes CVE-2025-66471 / GHSA-2xpw-w6gg-jr37 - Fixes CVE-2025-66418 / GHSA-gm62-xv2j-4w53 * Mon Dec 8 2025 Miro Hron\u010dok - 2.5.0-4 - Allow building with setuptools_scm 9

References


[ 1 ] Bug #2419408 - python-urllib3-2.6.1 is available https://bugzilla.redhat.com/show_bug.cgi?id=2419408 [ 2 ] Bug #2419493 - CVE-2025-6176 brotli: Brotli decompression bomb DoS in scrapy/scrapy [fedora-43] https://bugzilla.redhat.com/show_bug.cgi?id=2419493

Update Instructions

This update can be installed with the "dnf" update program. Use su -c 'dnf upgrade --advisory FEDORA-2025-d93200cf16' at the command line. For more information, refer to the dnf documentation available at http://dnf.readthedocs.io/en/latest/command_ref.html#upgrade-command-label

Severity
important
Lowest
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Name: python-urllib3
Product: Fedora 43
Version: 2.6.1
Release: 1.fc43
URL: https://github.com/urllib3/urllib3
Summary: HTTP library with thread-safe connection pooling, file post, and more

Topics%20covered

Topics Covered

security advisory denial of service fedora important python-urllib3 streaming api

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