Critical Security Flaw in Python 3.14: CPU Denial of Service Vulnerability
Summary
ALSA-2026:41949: Important: python3.14 security update. Affects python3.14 versions < 3.14.5-1.el9_8.1. Fixed in 3.14.5-1.el9_8.1. How to fix ↓
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Background
Python 3.14 is an interpreted, interactive, object-oriented programming language widely used for various applications, including web development, data analysis, artificial intelligence, and more. It features modules, classes, exceptions, and dynamic data types, making it versatile and powerful. However, a recent security vulnerability has been identified that could lead to a CPU Denial of Service (DoS) attack, affecting the stability and performance of applications relying on this version.
Vulnerability Detail
The vulnerability arises from a flaw in the HTML parser of Python 3.14, where repeated unterminated markup declarations can lead to excessive CPU usage. This can be exploited by attackers to create a denial of service condition, causing applications to hang or crash. The specific issue is tracked under CVE-2026-15308, which highlights the potential for significant disruption in services that utilize this version of Python.
How To Fix
Minimum fixed version
3.14.5-1.el9_8.1
This is the first release that contains the fix.
sudo dnf update python3.14Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider limiting the input to the HTML parser or implementing rate limiting on requests that utilize this parser to mitigate the risk of CPU overload until the update can be applied.
Conclusion
The identified vulnerability in Python 3.14 poses a significant risk of CPU Denial of Service attacks, which can severely impact applications using this version. It is crucial to apply the provided patch to mitigate this risk. Users are encouraged to monitor their applications for vulnerabilities using tools like Vulert, which can help ensure ongoing security.
See every vulnerability recorded for python3.14 →
FAQ
The vulnerability is a CPU Denial of Service issue caused by the HTML parser's handling of unterminated markup declarations.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Exploitation of this vulnerability can lead to application crashes or hangs, significantly affecting service availability and performance.
Yes, a patch is available in the form of an update to Python 3.14 version 3.14.5-1.el9_8.1.
If an immediate update is not possible, implement input restrictions or rate limiting on the HTML parser to reduce the risk of exploitation.
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