Critical Security Update for Python 3.14: CPU Denial of Service Vulnerability
Summary
ALSA-2026:40856: Important: python3.14 security update. Affects python3.14 versions < 3.14.5-1.el10_2.1. Fixed in 3.14.5-1.el10_2.1. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
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 high-level dynamic data types, making it versatile and powerful. However, it is susceptible to security vulnerabilities, such as the one identified in this advisory, which can lead to significant disruptions if not addressed promptly.
Vulnerability Detail
The vulnerability identified as CVE-2026-15308 is a CPU Denial of Service (DoS) issue in the HTML parser of Python 3.14. It arises from the handling of repeated unterminated markup declarations, which can cause excessive CPU usage, potentially leading to service outages. Attackers can exploit this vulnerability by sending specially crafted HTML content to the parser, resulting in a denial of service for legitimate users. The impact of this vulnerability can be severe, especially for applications relying on Python for web services or data processing.
How To Fix
Minimum fixed version
3.14.5-1.el10_2.1
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, avoid processing untrusted HTML content with the Python HTML parser until the update is applied. Implement input validation and sanitization to mitigate the risk of exploitation.
Conclusion
The vulnerability in Python 3.14, identified as CVE-2026-15308, poses a significant risk of CPU Denial of Service. It is crucial to update to the patched version 3.14.5-1.el10_2.1 to ensure the security and stability of applications relying on Python. Implementing workarounds and monitoring for vulnerabilities can help mitigate risks until updates are applied.
See every vulnerability recorded for python3.14 →
FAQ
CVE-2026-15308 is a vulnerability in Python 3.14 that allows for a CPU Denial of Service due to improper handling of unterminated markup declarations in the HTML parser.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which analyzes your manifest file for vulnerabilities.
The vulnerability can lead to excessive CPU usage, causing service outages and denial of service for legitimate users, impacting application availability.
Yes, a patch is available in the form of an updated package version 3.14.5-1.el10_2.1. It is recommended to update to this version to mitigate the risk.
If immediate updating is not possible, implement input validation and avoid processing untrusted HTML content to reduce the risk of exploitation.
Related vulnerabilities
Recent vulnerabilities recorded for python3.14.
