Improper handling of highly compressed data in urllib3 - CVE-2026-21441

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Main Vulnerability Database Vulnerabilities #VU121072

Improper handling of highly compressed data in urllib3 - CVE-2026-21441

Published: January 7, 2026 / Updated: February 17, 2026


Vulnerability identifier: #VU121072
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21441
CWE-ID: CWE-409
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to the application does not properly handle highly compressed data when sending HTTP redirect responses. A remote attacker can multiple large requests to the application, consume all available CPU and memory resources and perform a denial of service attack.


Affected software

urllib3
Debian Linux
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Manager Server
SUSE Manager Retail Branch Server
SUSE Manager Proxy
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Public Cloud Module
SUSE Linux Enterprise Server
SUSE Linux Enterprise Server for SAP Applications
Python 3 Module
Basesystem Module
openSUSE Leap
Ubuntu
openEuler
IBM Cloud Pak for Data System
cert-manager Operator for Red Hat OpenShift
PowerVC
IBM Fusion HCI
Splunk DB Connect
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data
IBM Watson Discovery for IBM Cloud Pak for Data
IBM Sterling Control Center
IBM Maximo Application Suite - Manage Component
IBM Maximo Application Suite
Red Hat OpenStack
Fusion Content-Aware Storage
Storage Sentinel Anomaly Scan Engine
Financial Transaction Manager for RedHat OpenShift
Security QRadar EDR
watsonx Code Assistant On Prem
Oracle Business Intelligence Enterprise Edition
Maximo Application Suite - Predict Component
Maximo Application Suite - Monitor Component
Maximo Application Suite - Edge Data Collector
Maximo Application Suite - Location Service for Esri Component
Maximo Application Suite - Visual Inspection Component
Maximo Application Suite Ai Service
Oracle Communications Policy Management
QRadar App SDK
Data Cataloging
Robotic Process Automation for Cloud Pak
Nautobot
watsonx.data
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
python-s3transfer (Red Hat package)
python-urllib3 (Red Hat package)
python3-urllib3
python-urllib3 (Ubuntu package)
python2-urllib3
python-urllib3
python3.11-urllib3 (Red Hat package)
python-urllib3 (Debian package)
python3.11-urllib3
python3.12-urllib3 (Red Hat package)
python311-urllib3_1
python3-urllib3-doc
python311-urllib3
resource-agents (Red Hat package)
fence-agents (Red Hat package)
resource-agents-paf
resource-agents-gcp
resource-agents-aliyun
resource-agents
python-pip (Ubuntu package)
python-pip
python3-pip
python-pip-help
python-pip-wheel
python2-pip
IBM InfoSphere Information Server
Oracle Communications Cloud Native Core Unified Data Repository
Oracle Communications Cloud Native Core Policy
Juniper Junos Space

How to mitigate CVE-2026-21441

Install updates from vendor's website.

urllib3 - update to 2.6.3
IBM Cloud Pak for Data System - update to 1.0.10.0
Fusion Content-Aware Storage - update to 1.1.3
Storage Sentinel Anomaly Scan Engine - update to 2.3.0
cert-manager Operator for Red Hat OpenShift - update to 1.18.1
Nautobot - addressed in versions 2.4.25, 3.0.4
watsonx.data - update to 2.3.1
IBM Fusion HCI - update to 2.13.0
Splunk DB Connect - update to 4.2.0
Security QRadar EDR - update to 3.12.24
IBM Watson Speech Services Cartridge for IBM Cloud Pak for Data - update to 5.3.1
IBM Watson Discovery for IBM Cloud Pak for Data - update to 5.3.1
watsonx Code Assistant On Prem - update to 5.3.1
IBM Sterling Control Center - addressed in versions 6.3.1.0.7, 6.4.1.0.1, 6.4.2.0.1
IBM Maximo Application Suite - Manage Component - addressed in versions 8.6.36, 8.7.30, 9.0.23, 9.1.11
Maximo Application Suite - Predict Component - addressed in versions 8.8.14, 8.9.16, 9.0.13, 9.1.6
IBM Maximo Application Suite - addressed in versions 8.10.36, 8.11.33, 9.0.22, 9.1.11
Maximo Application Suite - Monitor Component - addressed in versions 8.10.28, 8.11.26, 9.0.18, 9.1.8
Maximo Application Suite - Edge Data Collector - addressed in versions 8.11.26, 9.0.18, 9.1.8
Maximo Application Suite - Location Service for Esri Component - addressed in versions 9.0.7, 9.1.6
Maximo Application Suite - Visual Inspection Component - update to 9.1.10
Maximo Application Suite Ai Service - update to 9.1.11
IBM InfoSphere Information Server - update to 11.7.1.6 Service pack 1
python-s3transfer (Red Hat package) - update to 0.1.13-1.el7_9.6
python-urllib3 (Red Hat package) - addressed in versions 1.24.2-5.el8_4.1, 1.24.2-5.el8_6.4, 1.24.2-5.el8_8.3, 1.24.2-9.el8_10, 1.26.5-3.el8ost.3, 1.26.5-3.el9_0.2, 1.26.5-3.el9_2.3, 1.26.5-5.el9_4.3, 1.26.5-6.el9_6.1, 1.26.5-6.el9_7.1, 1.26.19-2.el10_0.1, 1.26.19-2.el10_1.1
python3-urllib3 - addressed in versions 1.24.2-9, 1.26.19-4
python-urllib3 (Ubuntu package) - addressed in versions 1.25.8-2ubuntu0.4+esm3, 1.25.8-2ubuntu0.4+esm4, 1.26.5-1~exp1ubuntu0.5, 1.26.5-1~exp1ubuntu0.6, 2.0.7-1ubuntu0.4, 2.3.0-2ubuntu0.3, 2.3.0-3ubuntu0.2
python2-urllib3 - update to 1.25.9-15
python3-urllib3 - addressed in versions 1.25.9-15, 1.26.12-11, 1.26.18-6
python-urllib3 - addressed in versions 1.25.9-15, 1.26.12-11, 1.26.18-6
python-urllib3 - update to 1.25.10-3.48.4
python3-urllib3 - addressed in versions 1.25.10-3.48.4, 1.25.10-150300.4.21.1
python3.11-urllib3 (Red Hat package) - addressed in versions 1.26.12-1.el8_8.3, 1.26.12-1.el9_2.2, 1.26.12-2.el9_4.3, 1.26.12-5.el9_6.1, 1.26.12-5.el9_7.1, 1.26.12-6.el8_10
python-urllib3 (Debian package) - addressed in versions 1.26.12-1+deb12u2, 2.3.0-3+deb13u1
python3.11-urllib3 - update to 1.26.12-6
python3.12-urllib3 (Red Hat package) - addressed in versions 1.26.18-2.el9_4.2, 1.26.19-1.el9_6.1, 1.26.19-1.el9_7.1, 1.26.19-2.el8_10
python311-urllib3_1 - update to 1.26.18-150600.3.6.1
python3-urllib3-doc - update to 1.26.19-4
python311-urllib3 - update to 2.0.7-150400.7.24.1
QRadar App SDK - update to 2.2.5
Data Cataloging - update to 2.5.3
resource-agents (Red Hat package) - addressed in versions 4.1.1-90.el8_4.22, 4.9.0-16.el8_6.19, 4.9.0-40.el8_8.15, 4.9.0-54.el8_10.27
fence-agents (Red Hat package) - addressed in versions 4.2.1-65.el8_4.25, 4.2.1-89.el8_6.20, 4.2.1-112.el8_8.15, 4.10.0-20.el9_0.27, 4.10.0-43.el9_2.18, 4.10.0-62.el9_4.21, 4.10.0-86.el9_6.14
resource-agents-paf - update to 4.9.0-54
resource-agents-gcp - update to 4.9.0-54
resource-agents-aliyun - update to 4.9.0-54
resource-agents - update to 4.9.0-54
python-pip (Ubuntu package) - addressed in versions 8.1.1-2ubuntu0.6+esm12, 9.0.1-2.3~ubuntu1.18.04.8+esm8, 20.0.2-5ubuntu1.11+esm4
Red Hat OpenStack - update to 17.1
python-pip - addressed in versions 20.2.2-15, 21.3.1-13, 21.3.1-15, 23.3.1-9
python3-pip - addressed in versions 20.2.2-15, 21.3.1-13, 21.3.1-15, 23.3.1-9
python-pip-help - addressed in versions 20.2.2-15, 21.3.1-13, 21.3.1-15, 23.3.1-9
python-pip-wheel - addressed in versions 20.2.2-15, 21.3.1-13, 21.3.1-15, 23.3.1-9
python2-pip - update to 20.2.2-15
Robotic Process Automation for Cloud Pak - addressed in versions 23.0.20.6, 30.0.2
python-pip-wheel - update to 23.3.1-8
python3-pip - update to 23.3.1-8
Juniper Junos Space - update to 26.1R1 Patch V1

External References

Related Security Bulletins