Critical Security Update for python-markdown: Denial of Service Vulnerability
Summary
ALSA-2026:19366: Important: python-markdown security update. Affects python3-markdown versions < 3.3.4-4.el9_8.2. Fixed in 3.3.4-4.el9_8.2. How to fix ↓
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Background
Python-markdown is a widely used library for converting Markdown text to HTML. It is an interpreted, interactive, object-oriented programming language that supports modules, classes, exceptions, and dynamic data types. This library is essential for developers who need to render Markdown content in their applications. However, it has been found to be vulnerable to a denial of service attack through malformed HTML-like sequences, which can disrupt the functionality of applications relying on it.
Vulnerability Detail
The vulnerability identified as CVE-2025-69534 allows attackers to exploit python-markdown by sending specially crafted input that contains malformed HTML-like sequences. This can lead to a denial of service, causing the application to crash or become unresponsive. The issue arises from improper handling of input, making it critical for developers to address this vulnerability promptly to maintain application stability and security.
How To Fix
Minimum fixed version
3.3.4-4.el9_8.2
This is the first release that contains the fix.
sudo dnf update python3-markdownTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can sanitize input data to prevent malformed HTML-like sequences from being processed by the python-markdown library. Implementing input validation can help mitigate the risk until the package is updated.
Conclusion
The python-markdown library has a critical vulnerability that can lead to denial of service attacks. It is essential for developers to update to the latest patched version to ensure application security. Implementing input validation can serve as a temporary measure until the update is applied.
See every vulnerability recorded for python3-markdown →
FAQ
CVE-2025-69534 is a vulnerability in the python-markdown library that allows for denial of service attacks through malformed HTML-like sequences.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The primary consequence of this vulnerability is that it can lead to a denial of service, causing applications to crash or become unresponsive.
Yes, a patch is available in version 3.3.4-4.el9_8.2 of the python3-markdown package.
If you cannot update the package immediately, implement input validation to sanitize data and prevent malformed sequences from being processed.
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