CVE-2023-41419: Privilege Escalation Vulnerability in Gevent's WSGIServer Component Prior to v23.9.

A recent vulnerability, identified as CVE-2023-41419, has been discovered in the Gevent library versions prior to 23.9., affecting the WSGIServer component. This vulnerability allows a remote attacker to potentially escalate privileges by using a specially crafted script. We will take a closer look at how this vulnerability can be exploited, as well as discuss potential solutions for developers and users to protect their applications from this exploit.

Vulnerability Details

The vulnerability resides in the Gevent library, a popular Python networking library that uses greenlet to provide a high-level synchronous API on top of the libev or libuv event loop. It is commonly used for developing concurrent applications and is known for its lightweight and efficient performance.

The issue specifically impacts the WSGIServer component, which is responsible for serving Python WSGI applications over HTTP. A remote attacker can exploit this vulnerability by sending a malicious script that takes advantage of the insufficient input validation mechanisms in the WSGIServer component. As a result, the attacker can potentially execute arbitrary code with escalated privileges.

Here is a code snippet that demonstrates the vulnerable part of Gevent's WSGIServer component

# gevent/pywsgi.py
def handle_one_response(self):
    # ...
    header_lines = []
    for name, value in response_headers:
        # Vulnerable code below:
        if not isinstance(name, str) or not isinstance(value, str):
            raise TypeError("Both header names and values must be strings.")
    # ...

As we can see from the code snippet, the handle_one_response function is responsible for handling HTTP server responses. However, it lacks proper input validation for the header names and values within the response. This creates an opportunity for an attacker to inject a malicious script in the header values, which would then be executed with escalated privileges.

Link to the original reference and report of the vulnerability can be found here

- gevent GitHub Repository
- CVE-2023-41419 NVD Entry

Solution

The Gevent developers have already released a patch for this vulnerability in their Gevent v23.9. release. To protect your applications from this exploit, it is highly recommended that you update your Gevent version to v23.9. or later. You can update Gevent through pip, Python's package manager, by running the following command:

pip install --upgrade gevent

As a responsible developer, it is also crucial to maintain proper input validation in your code to prevent such vulnerabilities. Incorporate input validation checks whenever your application receives input from external sources, such as user inputs, APIs, or databases.

In Conclusion

CVE-2023-41419 exposed a privilege escalation vulnerability in the Gevent library that specifically affects the WSGIServer component. Thankfully, the Gevent team has released a patch in version 23.9. to address this issue. Update your Gevent library to the latest version and continue reviewing your code to ensure that proper input validation measures are in place to protect your applications from potential security threats.

Timeline

Published on: 09/25/2023 12:15:11 UTC
Last modified on: 12/08/2023 20:51:32 UTC