Bug 2427726 (CVE-2026-21441) - CVE-2026-21441 urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)
Summary: CVE-2026-21441 urllib3: urllib3 vulnerable to decompression-bomb safeguard by...
Keywords:
Status: NEW
Alias: CVE-2026-21441
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2428730 2428731 2431307 2428642 2428643 2428644 2428645 2428646 2428647 2428648 2428649 2428650 2428651 2431305 2431306 2431309 2431310
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-01-07 23:02 UTC by OSIDB Bzimport
Modified: 2026-02-02 17:41 UTC (History)
167 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2026:1301 0 None None None 2026-01-26 23:37:41 UTC
Red Hat Product Errata RHBA-2026:1728 0 None None None 2026-02-02 17:00:26 UTC
Red Hat Product Errata RHSA-2026:1086 0 None None None 2026-01-26 12:38:33 UTC
Red Hat Product Errata RHSA-2026:1087 0 None None None 2026-01-26 12:59:49 UTC
Red Hat Product Errata RHSA-2026:1088 0 None None None 2026-01-26 14:15:00 UTC
Red Hat Product Errata RHSA-2026:1089 0 None None None 2026-01-26 14:06:37 UTC
Red Hat Product Errata RHSA-2026:1224 0 None None None 2026-01-26 14:58:14 UTC
Red Hat Product Errata RHSA-2026:1226 0 None None None 2026-01-26 15:29:48 UTC
Red Hat Product Errata RHSA-2026:1239 0 None None None 2026-01-26 17:59:30 UTC
Red Hat Product Errata RHSA-2026:1240 0 None None None 2026-01-26 18:14:08 UTC
Red Hat Product Errata RHSA-2026:1241 0 None None None 2026-01-26 17:55:08 UTC
Red Hat Product Errata RHSA-2026:1254 0 None None None 2026-01-26 20:44:29 UTC
Red Hat Product Errata RHSA-2026:1485 0 None None None 2026-01-28 11:22:02 UTC
Red Hat Product Errata RHSA-2026:1546 0 None None None 2026-01-29 09:08:48 UTC
Red Hat Product Errata RHSA-2026:1618 0 None None None 2026-02-02 01:12:54 UTC
Red Hat Product Errata RHSA-2026:1619 0 None None None 2026-02-02 01:53:24 UTC
Red Hat Product Errata RHSA-2026:1674 0 None None None 2026-02-02 06:38:23 UTC
Red Hat Product Errata RHSA-2026:1676 0 None None None 2026-02-02 06:49:38 UTC
Red Hat Product Errata RHSA-2026:1693 0 None None None 2026-02-02 09:57:11 UTC
Red Hat Product Errata RHSA-2026:1704 0 None None None 2026-02-02 11:45:28 UTC
Red Hat Product Errata RHSA-2026:1706 0 None None None 2026-02-02 12:28:18 UTC
Red Hat Product Errata RHSA-2026:1712 0 None None None 2026-02-02 13:06:03 UTC
Red Hat Product Errata RHSA-2026:1717 0 None None None 2026-02-02 14:02:10 UTC
Red Hat Product Errata RHSA-2026:1726 0 None None None 2026-02-02 15:19:04 UTC
Red Hat Product Errata RHSA-2026:1729 0 None None None 2026-02-02 15:38:41 UTC
Red Hat Product Errata RHSA-2026:1734 0 None None None 2026-02-02 17:37:58 UTC
Red Hat Product Errata RHSA-2026:1735 0 None None None 2026-02-02 17:41:53 UTC

Description OSIDB Bzimport 2026-01-07 23:02:25 UTC
urllib3 is an HTTP client library for Python. 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. 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.

Comment 1 errata-xmlrpc 2026-01-26 12:38:23 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:1086 https://access.redhat.com/errata/RHSA-2026:1086

Comment 2 errata-xmlrpc 2026-01-26 12:59:37 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:1087 https://access.redhat.com/errata/RHSA-2026:1087

Comment 3 errata-xmlrpc 2026-01-26 14:06:26 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:1089 https://access.redhat.com/errata/RHSA-2026:1089

Comment 4 errata-xmlrpc 2026-01-26 14:14:47 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:1088 https://access.redhat.com/errata/RHSA-2026:1088

Comment 5 errata-xmlrpc 2026-01-26 14:58:02 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:1224 https://access.redhat.com/errata/RHSA-2026:1224

Comment 6 errata-xmlrpc 2026-01-26 15:29:36 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:1226 https://access.redhat.com/errata/RHSA-2026:1226

Comment 7 errata-xmlrpc 2026-01-26 17:54:57 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:1241 https://access.redhat.com/errata/RHSA-2026:1241

Comment 8 errata-xmlrpc 2026-01-26 17:59:20 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:1239 https://access.redhat.com/errata/RHSA-2026:1239

Comment 9 errata-xmlrpc 2026-01-26 18:13:58 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:1240 https://access.redhat.com/errata/RHSA-2026:1240

Comment 10 errata-xmlrpc 2026-01-26 20:44:19 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:1254 https://access.redhat.com/errata/RHSA-2026:1254

Comment 11 errata-xmlrpc 2026-01-28 11:21:51 UTC
This issue has been addressed in the following products:

  RHUI 4 for RHEL 8

Via RHSA-2026:1485 https://access.redhat.com/errata/RHSA-2026:1485

Comment 12 errata-xmlrpc 2026-01-29 09:08:38 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:1546 https://access.redhat.com/errata/RHSA-2026:1546

Comment 13 errata-xmlrpc 2026-02-02 01:12:42 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2026:1618 https://access.redhat.com/errata/RHSA-2026:1618

Comment 14 errata-xmlrpc 2026-02-02 01:53:12 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:1619 https://access.redhat.com/errata/RHSA-2026:1619

Comment 15 errata-xmlrpc 2026-02-02 06:38:12 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Extended Update Support

Via RHSA-2026:1674 https://access.redhat.com/errata/RHSA-2026:1674

Comment 16 errata-xmlrpc 2026-02-02 06:49:28 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:1676 https://access.redhat.com/errata/RHSA-2026:1676

Comment 17 errata-xmlrpc 2026-02-02 09:57:00 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:1693 https://access.redhat.com/errata/RHSA-2026:1693

Comment 18 errata-xmlrpc 2026-02-02 11:45:17 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:1704 https://access.redhat.com/errata/RHSA-2026:1704

Comment 19 errata-xmlrpc 2026-02-02 12:28:07 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:1706 https://access.redhat.com/errata/RHSA-2026:1706

Comment 20 errata-xmlrpc 2026-02-02 13:05:51 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Extended Update Support

Via RHSA-2026:1712 https://access.redhat.com/errata/RHSA-2026:1712

Comment 21 errata-xmlrpc 2026-02-02 14:01:59 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Extended Update Support

Via RHSA-2026:1717 https://access.redhat.com/errata/RHSA-2026:1717

Comment 22 errata-xmlrpc 2026-02-02 15:18:51 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:1726 https://access.redhat.com/errata/RHSA-2026:1726

Comment 23 errata-xmlrpc 2026-02-02 15:38:29 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:1729 https://access.redhat.com/errata/RHSA-2026:1729

Comment 24 errata-xmlrpc 2026-02-02 17:37:47 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions

Via RHSA-2026:1734 https://access.redhat.com/errata/RHSA-2026:1734

Comment 25 errata-xmlrpc 2026-02-02 17:41:41 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:1735 https://access.redhat.com/errata/RHSA-2026:1735


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