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Ubuntu: urllib3 Important Denial of Service CVE-2026-21441

ubuntu
Calendar Grey January 12, 2026
Dist Ubuntu Esm H88
Update your Ubuntu system to fix the urllib3 resource exhaustion issue causing potential DoS attacks.
urllib3 could be made to use excessive resources if it received specially crafted network traffic.

Summary

A security issue affects these releases of Ubuntu and its derivatives: - Ubuntu 25.10 - Ubuntu 25.04 - Ubuntu 24.04 LTS - Ubuntu 22.04 LTS - Ubuntu 20.04 LTS Summary: urllib3 could be made to use excessive resources if it received specially crafted network traffic. Software Description: - python-urllib3: HTTP library with thread-safe connection pooling Details: It was discovered that urllib3 incorrectly handled decompression during HTTP redirects. An attacker could possibly use this issue to cause urllib3 to use excessive resources, causing a denial of service.

Topics%20covered

Topics Covered

security advisory DoS Ubuntu important resource exhaustion urllib3

Update Instructions

The problem can be corrected by updating your system to the following package versions: Ubuntu 25.10 python3-urllib3 2.3.0-3ubuntu0.2 Ubuntu 25.04 python3-urllib3 2.3.0-2ubuntu0.3 Ubuntu 24.04 LTS python3-urllib3 2.0.7-1ubuntu0.4 Ubuntu 22.04 LTS python3-urllib3 1.26.5-1~exp1ubuntu0.5 Ubuntu 20.04 LTS python3-urllib3 1.25.8-2ubuntu0.4+esm3 Available with Ubuntu Pro In general, a standard system update will make all the necessary changes.

References

https://ubuntu.com/security/notices/USN-7955-1

CVE-2026-21441

Severity
important
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-7955-1

Topics%20covered

Topics Covered

security advisory DoS Ubuntu important resource exhaustion urllib3

Package Information

https://launchpad.net/ubuntu/+source/python-urllib3/2.3.0-3ubuntu0.2 https://launchpad.net/ubuntu/+source/python-urllib3/2.3.0-2ubuntu0.3 https://launchpad.net/ubuntu/+source/python-urllib3/2.0.7-1ubuntu0.4 https://launchpad.net/ubuntu/+source/python-urllib3/1.26.5-1~exp1ubuntu0.5

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