RHSA-2026:1086 - Security Advisory

Topic

An update for python-urllib3 is now available for Red Hat Enterprise Linux 10.

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.

Description

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.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux for x86_64 10 x86_64
• Red Hat Enterprise Linux for IBM z Systems 10 s390x
• Red Hat Enterprise Linux for Power, little endian 10 ppc64le
• Red Hat Enterprise Linux for ARM 64 10 aarch64

Fixes

• BZ - 2419455 - CVE-2025-66418 urllib3: urllib3: Unbounded decompression chain leads to resource exhaustion
• BZ - 2419467 - CVE-2025-66471 urllib3: urllib3 Streaming API improperly handles highly compressed data
• BZ - 2427726 - CVE-2026-21441 urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)

CVEs

• CVE-2025-66418
• CVE-2025-66471
• CVE-2026-21441

References

• https://access.redhat.com/security/updates/classification/#important