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@renovate renovate bot commented Jan 8, 2026

This PR contains the following updates:

Package Change Age Confidence
urllib3 (changelog) ==2.6.2==2.6.3 age confidence
urllib3 (changelog) ==2.5.0==2.6.3 age confidence

GitHub Vulnerability Alerts

CVE-2026-21441

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.

urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption.

However, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client (high CPU usage and large memory allocations for decompressed data; CWE-409).

Affected usages

Applications and libraries using urllib3 version 2.6.2 and earlier to stream content from untrusted sources by setting preload_content=False when they do not disable redirects.

Remediation

Upgrade to at least urllib3 v2.6.3 in which the library does not decode content of redirect responses when preload_content=False.

If upgrading is not immediately possible, disable redirects by setting redirect=False for requests to untrusted source.


Release Notes

urllib3/urllib3 (urllib3)

v2.6.3

Compare Source

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

  • Fixed a high-severity security issue where decompression-bomb safeguards of
    the streaming API were bypassed when HTTP redirects were followed.
    (GHSA-38jv-5279-wg99 <https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99>__)
  • Started treating Retry-After times greater than 6 hours as 6 hours by
    default. (#&#8203;3743 <https://github.com/urllib3/urllib3/issues/3743>__)
  • Fixed urllib3.connection.VerifiedHTTPSConnection on Emscripten.
    (#&#8203;3752 <https://github.com/urllib3/urllib3/issues/3752>__)

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@renovate renovate bot added dependencies use for pull requests that update a dependency file filigran team use to identify PR from the Filigran team labels Jan 8, 2026
@renovate renovate bot force-pushed the renovate/pypi-urllib3-vulnerability branch from bff0b85 to 93e38cd Compare January 8, 2026 10:14
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Fix Security alerts

image

@helene-nguyen helene-nguyen merged commit c61ed95 into master Jan 9, 2026
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@helene-nguyen helene-nguyen deleted the renovate/pypi-urllib3-vulnerability branch January 9, 2026 08:41
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