RHSA-2026:1726

Vulnerability from csaf_redhat - Published: 2026-02-02 15:25 - Updated: 2026-02-11 21:20
Summary
Red Hat Security Advisory: python-urllib3 security update

Notes

Topic
An update for python-urllib3 is now available for Red Hat Enterprise Linux 10.0 Extended Update Support. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.
Details
Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems. Security Fix(es): * urllib3: urllib3: Unbounded decompression chain leads to resource exhaustion (CVE-2025-66418) * urllib3: urllib3 Streaming API improperly handles highly compressed data (CVE-2025-66471) * urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) (CVE-2026-21441) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Terms of Use
This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
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          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
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          "text": "2427726"
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      "notes": [
        {
          "category": "description",
          "text": "urllib3 is an HTTP client library for Python. urllib3\u0027s 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. Starting in version 1.22 and prior to version 2.6.3, 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. Applications and libraries are affected when they stream content from untrusted sources by setting `preload_content=False` when they do not disable redirects. Users should 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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          "product_ids": [
            "BaseOS-10.0.Z.E2S:python-urllib3-0:1.26.19-2.el10_0.1.src",
            "BaseOS-10.0.Z.E2S:python3-urllib3-0:1.26.19-2.el10_0.1.noarch"
          ],
          "restart_required": {
            "category": "none"
          },
          "url": "https://access.redhat.com/errata/RHSA-2026:1726"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
            "BaseOS-10.0.Z.E2S:python-urllib3-0:1.26.19-2.el10_0.1.src",
            "BaseOS-10.0.Z.E2S:python3-urllib3-0:1.26.19-2.el10_0.1.noarch"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)"
    }
  ]
}


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Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.