Security update for python-urllib3_1 SUSE Patch security@suse.de SUSE Security Team SUSE-SU-2026:0635-1 Final 1 1 2026-02-25T11:12:53Z current 2026-02-25T11:12:53Z 2026-02-25T11:12:53Z cve-database/bin/generate-cvrf.pl 2017-02-24T01:00:00Z Security update for python-urllib3_1 This update for python-urllib3_1 fixes the following issues: - CVE-2025-66471: excessive resource consumption via decompression of highly compressed data in Streaming API (bsc#1254867). - CVE-2025-66418: resource exhaustion via unbounded number of links in the decompression chain (bsc#1254866). - CVE-2026-21441: excessive resource consumption during decompression of data in HTTP redirect responses (bsc#1256331). The CVRF data is provided by SUSE under the Creative Commons License 4.0 with Attribution (CC-BY-4.0). SUSE-2026-635,SUSE-SLE-Module-Python3-15-SP7-2026-635,openSUSE-SLE-15.6-2026-635 Copyright SUSE LLC under the Creative Commons License 4.0 with Attribution (CC-BY-4.0) https://www.suse.com/support/update/announcement/2026/suse-su-20260635-1/ Link for SUSE-SU-2026:0635-1 https://lists.suse.com/pipermail/sle-security-updates/2026-February/024387.html E-Mail link for SUSE-SU-2026:0635-1 https://www.suse.com/support/security/rating/ SUSE Security Ratings https://bugzilla.suse.com/1254866 SUSE Bug 1254866 https://bugzilla.suse.com/1254867 SUSE Bug 1254867 https://bugzilla.suse.com/1256331 SUSE Bug 1256331 https://www.suse.com/security/cve/CVE-2025-66418/ SUSE CVE CVE-2025-66418 page https://www.suse.com/security/cve/CVE-2025-66471/ SUSE CVE CVE-2025-66471 page https://www.suse.com/security/cve/CVE-2026-21441/ SUSE CVE CVE-2026-21441 page SUSE Linux Enterprise Module for Python 3 15 SP7 openSUSE Leap 15.6 python311-urllib3_1-1.26.18-150600.3.6.1 python311-urllib3_1-1.26.18-150600.3.6.1 as a component of SUSE Linux Enterprise Module for Python 3 15 SP7 python311-urllib3_1-1.26.18-150600.3.6.1 as a component of openSUSE Leap 15.6 urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, 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. This vulnerability is fixed in 2.6.0. CVE-2025-66418 SUSE Linux Enterprise Module for Python 3 15 SP7:python311-urllib3_1-1.26.18-150600.3.6.1 openSUSE Leap 15.6:python311-urllib3_1-1.26.18-150600.3.6.1 moderate To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2026/suse-su-20260635-1/ https://www.suse.com/security/cve/CVE-2025-66418.html CVE-2025-66418 https://bugzilla.suse.com/1254866 SUSE Bug 1254866 urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.0 and prior to 2.6.0, the Streaming API improperly handles highly compressed data. 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. CVE-2025-66471 SUSE Linux Enterprise Module for Python 3 15 SP7:python311-urllib3_1-1.26.18-150600.3.6.1 openSUSE Leap 15.6:python311-urllib3_1-1.26.18-150600.3.6.1 moderate To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2026/suse-su-20260635-1/ https://www.suse.com/security/cve/CVE-2025-66471.html CVE-2025-66471 https://bugzilla.suse.com/1254867 SUSE Bug 1254867 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. CVE-2026-21441 SUSE Linux Enterprise Module for Python 3 15 SP7:python311-urllib3_1-1.26.18-150600.3.6.1 openSUSE Leap 15.6:python311-urllib3_1-1.26.18-150600.3.6.1 moderate To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch". https://www.suse.com/support/update/announcement/2026/suse-su-20260635-1/ https://www.suse.com/security/cve/CVE-2026-21441.html CVE-2026-21441 https://bugzilla.suse.com/1256331 SUSE Bug 1256331