chore(deps): update dependency urllib3 to v2.6.0 [security]

[renovate-bot]

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.

CVE-2025-66471

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation.

The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side, even if the application only requested a small chunk of data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier to stream large compressed responses or content from untrusted sources.

stream(), read(amt=256), read1(amt=256), read_chunked(amt=256), readinto(b) are examples of urllib3.HTTPResponse method calls using the affected logic unless decoding is disabled explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library avoids decompressing data that exceeds the requested amount.

If your environment contains a package facilitating the Brotli encoding, upgrade to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 too. These versions are enforced by the urllib3[brotli] extra in the patched versions of urllib3.

Credits

The issue was reported by @​Cycloctane.
Supplemental information was provided by @​stamparm during a security audit performed by 7ASecurity and facilitated by OSTIF.

---

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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---

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[gemini-code-assist]

Summary of Changes

Hello @renovate-bot, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request performs a vital update of the urllib3 Python library to version 2.6.0. The primary motivation for this upgrade is to patch significant security vulnerabilities, specifically one that could lead to a denial of service through malicious HTTP content encoding and another that prevents 'decompression bomb' attacks. This ensures the application remains robust against known exploits while also benefiting from general enhancements and bug fixes introduced in the new urllib3 release.

Highlights

• Security Update for urllib3: This pull request updates the urllib3 dependency from version 2.5.0 to 2.6.0 to address critical security vulnerabilities, including CVE-2025-66418 which mitigates a potential denial of service attack due to unbounded chained HTTP encoding.
• Decompression Bomb Fix: The update also includes a fix for a security issue where streaming APIs could improperly handle highly compressed HTTP content, preventing 'decompression bombs' and excessive resource consumption.
• General Improvements and Bug Fixes: Beyond security, urllib3 v2.6.0 introduces new features like byte key support in HTTPHeaderDict, improved string representations, and Python 3.14 free-threading support, alongside various bug fixes and minor removals.

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[gemini-code-assist]

Code Review

This pull request correctly updates the urllib3 dependency to version 2.6.0 to address the security vulnerability CVE-2025-66418. This is a crucial update. I have added one high-severity comment highlighting a breaking change in this new version of urllib3 that could potentially cause failures if deprecated methods are being used in the codebase. It is recommended to review this before merging.

[gemini-code-assist]

This update to urllib3 v2.6.0 introduces a breaking change by removing the deprecated HTTPResponse.getheaders() and getheader() methods. Direct usage of these methods in the codebase will lead to failures after this upgrade. The recommended replacements are response.headers and response.headers.get() respectively.