CVE-2024-7592 in Python: how cookie parsing can consume CPU

Published on 2026-10-27 by frfrand

A DoS in Python's http.cookies: what quadratic complexity is, how it was detected, where it affects, and what to update.

Can a cookie slow down an API?

Yes. Normally cookies are small data that accompany HTTP requests. But when their format is processed with an inefficient algorithm, a specially crafted input can demand too much work from the server. CVE-2024-7592 describes that problem in the standard http.cookies module of CPython.

What was failing?

When parsing cookie values with certain escape characters, the parser could perform quadratic complexity work: if an input grew, the time needed to process it increased disproportionately. This is known as algorithmic abuse or denial of service by CPU consumption. It is not an authentication problem nor remote code execution.

Who discovered it and how was it fixed?

The incident was recorded in the CPython project in issue #123067 in August 2024, with behavior tests of the http.cookies._unquote() method. The community prepared a change to avoid the problematic complexity. The Python security advisory, distributed by Seth Larson, classified the problem in its communication as low severity. Some databases may show another label based on different criteria; when prioritizing, it is advisable to look at the actual scope.

How could someone exploit it?

An attacker capable of sending HTTP headers or inputs processed by the affected function could cause the server to dedicate more CPU than expected to analyzing a value. If the application accepts enough requests and limits allow it, the service may become slow or stop responding. Execution depends on data passing through the vulnerable function; not all programs written in Python use it.

Does it affect Django, Flask, or FastAPI?

The technical report also examined scenarios where a framework uses Python's cookie parser. That does not mean all apps in each framework were exploitable. The chosen parser, HTTP server limits, and intermediate components must be studied. An API that does not use that path may not be exposed.

Where was the fix published?

Python incorporated fixes in its September 2024 security updates, including releases 3.12.6, 3.11.10, 3.10.15, 3.9.20, and 3.8.20. Those versions document the first fix in historical branches, not what to install in 2026. I preferred a current line and the patches maintained by your distribution.

How to review a system?

Check the Python version in each environment (production, containers, tasks), the code that uses cookies, and the header size rules applied by proxy and server. Check if CPU spikes coincide with anomalous requests. Perform performance tests only in a controlled environment and with inputs of reasonable size, without sending aggressive loads to public services.

How is it mitigated?

Update the interpreter and rebuild images or virtual environments so they actually use a fixed version. Configure header limits, timeouts, and service capacity according to your needs; add metrics and alerts. A proxy can help, but it does not replace fixing the parser.

Frequently asked questions

Does CVE-2024-7592 allow session theft? The documented failure is CPU consumption, not cookie leakage.

Do I have to change Django? It depends on the path and how it reaches the standard library; updating Python is central.

Why does a low severity vulnerability matter? Because a small inefficiency can affect availability if the service is exposed or very sensitive to latency.

Sources: Official Python security announcement · CPython Issue #123067 · September 2024 releases.

Where is the information updated and how to request guidance?

At ArduMaker — CVE and support we maintain information to review incidents and channel inquiries, especially in WordPress and the technologies that run it. To evaluate a specific case, provide technology, version, operating system, deployment mode, and relevant error messages without publishing credentials. An announced CVE does not mean that all systems are compromised.

Editorial review: October 27, 2026. Recommendations may change with new manufacturer publications.

Practical example: a harmless cookie and a vulnerable parser

Situation: a Python application transforms the Cookie header into session data. Although most values are small, CVE-2024-7592 showed that certain inputs can cause the parser to consume too much CPU.

To understand the component without simulating an attack:

from http.cookies import SimpleCookie

cookies = SimpleCookie()
cookies.load("idioma=es; tema=oscuro")
print({nombre: item.value for nombre, item in cookies.items()})

Before: old runtime and absence of limits and observability. After: corrected Python in the executed environment, header size limits on the front-end server, and CPU and latency metrics.

Investigation example: if you see CPU spikes related to HTTP requests, cross-reference proxy logs with application processing times. Do not attribute every spike to this CVE: look for the affected version and actual use of http.cookies.

To avoid confusion: this vulnerability refers to availability, not to stealing passwords from cookies.