⬆️ Upgrade dependency urllib3 to v2.6.0 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
urllib3 (changelog)	==2.5.0 -> ==2.6.0

GitHub Vulnerability Alerts

CVE-2025-66418

Impact

urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, zstd).

However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier for HTTP requests to untrusted sources unless they disable content decoding explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library limits the number of links to 5.

If upgrading is not immediately possible, use preload_content=False and ensure that resp.headers["content-encoding"] contains a safe number of encodings before reading the response content.

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Release Notes

urllib3/urllib3 (urllib3)

v2.6.0

Compare Source

==================

Security

• 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.
  (GHSA-2xpw-w6gg-jr37 <https://github.com/urllib3/urllib3/security/advisories/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.
  (GHSA-gm62-xv2j-4w53 <https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53>__)

.. caution::

• If urllib3 is not installed with the optional urllib3[brotli] extra, but
  your environment contains a Brotli/brotlicffi/brotlipy package anyway, make
  sure to upgrade it to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 to
  benefit from the security fixes and avoid warnings. Prefer using
  urllib3[brotli] to install a compatible Brotli package automatically.

• If you use custom decompressors, please make sure to update them to
  respect the changed API of urllib3.response.ContentDecoder.

Features

• Enabled retrieval, deletion, and membership testing in HTTPHeaderDict using bytes keys. (#&#8203;3653 <https://github.com/urllib3/urllib3/issues/3653>__)
• Added host and port information to string representations of HTTPConnection. (#&#8203;3666 <https://github.com/urllib3/urllib3/issues/3666>__)
• Added support for Python 3.14 free-threading builds explicitly. (#&#8203;3696 <https://github.com/urllib3/urllib3/issues/3696>__)

Removals

• Removed the HTTPResponse.getheaders() method in favor of HTTPResponse.headers.
  Removed the HTTPResponse.getheader(name, default) method in favor of HTTPResponse.headers.get(name, default). (#&#8203;3622 <https://github.com/urllib3/urllib3/issues/3622>__)

Bugfixes

• Fixed redirect handling in urllib3.PoolManager when an integer is passed
  for the retries parameter. (#&#8203;3649 <https://github.com/urllib3/urllib3/issues/3649>__)
• Fixed HTTPConnectionPool when used in Emscripten with no explicit port. (#&#8203;3664 <https://github.com/urllib3/urllib3/issues/3664>__)
• Fixed handling of SSLKEYLOGFILE with expandable variables. (#&#8203;3700 <https://github.com/urllib3/urllib3/issues/3700>__)

Misc

• Changed the zstd extra to install backports.zstd instead of zstandard on Python 3.13 and before. (#&#8203;3693 <https://github.com/urllib3/urllib3/issues/3693>__)
• Improved the performance of content decoding by optimizing BytesQueueBuffer class. (#&#8203;3710 <https://github.com/urllib3/urllib3/issues/3710>__)
• Allowed building the urllib3 package with newer setuptools-scm v9.x. (#&#8203;3652 <https://github.com/urllib3/urllib3/issues/3652>__)
• Ensured successful urllib3 builds by setting Hatchling requirement to >= 1.27.0. (#&#8203;3638 <https://github.com/urllib3/urllib3/issues/3638>__)

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