Critical Security Update for python3-lxml: URL Bypass Vulnerability

python3-lxml Updated 17 Sep 2026

Summary

16/09/2026

Disclosed on

N/A

Severity

Yes i

Fix available

Unrated

Severity

Not published

CVSS Score

ALSA-2026:67943: Important: python-lxml security update. Affects python3-lxml versions < 4.2.3-5.el8_10. Fixed in 4.2.3-5.el8_10. How to fix ↓

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Background

Python3-lxml is a powerful library that provides a convenient API for processing XML and HTML documents. It is widely used for web scraping, data manipulation, and generating XML/HTML content. The library supports various features like XPath, XSLT, and HTML cleaning. However, it has recently been identified to have a security vulnerability that could allow attackers to bypass URL restrictions, potentially leading to unauthorized access or data exposure.

Vulnerability Detail

The vulnerability, identified as CVE-2026-49825, is a URL bypass issue in the lxml-html-clean module of python3-lxml. This flaw arises from a missing xlink:href attribute in the Cleaner class, which can be exploited by attackers to manipulate URLs and gain access to restricted resources. The ramifications of this vulnerability include unauthorized data access and potential exploitation of web applications that rely on this library for HTML cleaning.

How To Fix

Minimum fixed version

4.2.3-5.el8_10

This is the first release that contains the fix.

sudo dnf update python3-lxml

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Workaround

As a temporary workaround, you can avoid using the lxml-html-clean module until the package is updated. Additionally, ensure that your application implements strict validation and sanitization of URLs to mitigate the risk of exploitation.

Conclusion

The python3-lxml library has a critical vulnerability that could lead to unauthorized access through URL bypass. It is essential to update to the latest patched version to secure your applications. Additionally, utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.

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