fix(deps): update dependency urllib3 to >=1.26.20,<2 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
urllib3 (changelog)	>=1.26.18,<2 → >=1.26.20,<2

GitHub Vulnerability Alerts

CVE-2025-50181

urllib3 handles redirects and retries using the same mechanism, which is controlled by the Retry object. The most common way to disable redirects is at the request level, as follows:

resp = urllib3.request("GET", "https://httpbin.org/redirect/1", redirect=False)
print(resp.status)

# 302

However, it is also possible to disable redirects, for all requests, by instantiating a PoolManager and specifying retries in a way that disable redirects:

import urllib3

http = urllib3.PoolManager(retries=0)  # should raise MaxRetryError on redirect
http = urllib3.PoolManager(retries=urllib3.Retry(redirect=0))  # equivalent to the above
http = urllib3.PoolManager(retries=False)  # should return the first response

resp = http.request("GET", "https://httpbin.org/redirect/1")

However, the retries parameter is currently ignored, which means all the above examples don't disable redirects.

Affected usages

Passing retries on PoolManager instantiation to disable redirects or restrict their number.

By default, requests and botocore users are not affected.

Impact

Redirects are often used to exploit SSRF vulnerabilities. An application attempting to mitigate SSRF or open redirect vulnerabilities by disabling redirects at the PoolManager level will remain vulnerable.

Remediation

You can remediate this vulnerability with the following steps:

• Upgrade to a patched version of urllib3. If your organization would benefit from the continued support of urllib3 1.x, please contact sethmichaellarson@gmail.com to discuss sponsorship or contribution opportunities.
• Disable redirects at the request() level instead of the PoolManager() level.

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.

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.

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Release Notes

urllib3/urllib3 (urllib3)

v1.26.20

Compare Source

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

• Fixed a crash where certain standard library hash functions were absent in
  FIPS-compliant environments.
  (#&#8203;3432 <https://github.com/urllib3/urllib3/issues/3432>__)
• Replaced deprecated dash-separated setuptools entries in setup.cfg.
  (#&#8203;3461 <https://github.com/urllib3/urllib3/pull/3461>__)
• Took into account macOS setting ECONNRESET instead of EPROTOTYPE in
  its newer versions.
  (#&#8203;3416 <https://github.com/urllib3/urllib3/pull/3416>__)
• Backported changes to our tests and CI configuration from v2.x to support
  testing with CPython 3.12 and 3.13.
  (#&#8203;3436 <https://github.com/urllib3/urllib3/pull/3436>__)

v1.26.19

Compare Source

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

• Added the Proxy-Authorization header to the list of headers to strip from requests when redirecting to a different host. As before, different headers can be set via Retry.remove_headers_on_redirect.
• Fixed handling of OpenSSL 3.2.0 new error message for misconfiguring an HTTP proxy as HTTPS. (#&#8203;3405 <https://github.com/urllib3/urllib3/issues/3405>__)

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