CVE-2022-22817: Arbitrary Expression Evaluation in PIL.ImageMath.eval of Pillow Before 9.., Exec Method Exploit, and Lambda Expression Use

CVE-2022-22817 is a significant and potentially dangerous vulnerability present in the popular Python imaging library, Pillow, in versions 9.. and earlier. This vulnerability results from the improper handling of arbitrary expressions permitted in the PIL.ImageMath.eval() function. Malicious users could exploit this vulnerability by utilizing the Python exec method or a lambda expression to execute arbitrary code through unsuspecting programs that implement Pillow.

Pillow: Overview

Pillow is a user-friendly, powerful, and fast image-processing library for Python. It is a fork of the original Python Imaging Library (PIL) and adds extended capabilities for image manipulation and processing. Users can perform various tasks, including image cropping, resizing, rotating, color transformations, and many more.

Code Snippet: Vulnerability Demonstration

The following code snippet demonstrates the arbitrary expression evaluation vulnerability in the PIL.ImageMath.eval() function:

import PIL.ImageMath

malicious_code = "exec('import os; os.system(\"touch exploit.txt\")')"
payload = f"lambda: {malicious_code}"
PIL.ImageMath.eval(payload)

In this example, the eval() function evaluates payload as if it were lambda expression provided by the user. However, the malicious_code includes an exec() call that could execute arbitrary commands on the host system. In our example, it creates an empty file named exploit.txt, indicating a successful exploit.

Exploit Details

An attacker can craft a malicious payload containing arbitrary Python code and inject it into an application that uses the vulnerable version of the Pillow library. When the application attempts to process an image using the PIL.ImageMath.eval() function, the attacker's chosen code is executed, compromising the security of the system and allowing for potential malicious activities such as data breaches and system hijacking.

Original References and Resources

- CVE Details: https://nvd.nist.gov/vuln/detail/CVE-2022-22817
- National Vulnerability Database (NVD): https://nvd.nist.gov/
- Pillow Documentation: https://pillow.readthedocs.io/en/stable/index.html

Mitigation and Protection

To protect your application from being exploited through this vulnerability, it is crucial that you follow these steps:

Update your Pillow library

Ensure you are using the latest and most secure version of the Pillow library. At the time of writing, that is version 9.. or higher.

Input Validation

Sanitize any input that is expected to be used as lambda expressions in the PIL.ImageMath.eval() function. Validate and restrict expressions to make sure they do not include dangerous elements, such as exec, os, and other potentially harmful code.

Keep yourself informed

Stay up-to-date on security news, vulnerabilities, and patches related to the libraries and frameworks used in your project. Regularly check repositories, mailing lists, and developer communities for information and timely updates.

Conclusion

CVE-2022-22817 is a severe vulnerability affecting the Pillow library, allowing arbitrary expression evaluation and potentially introducing harmful consequences in projects that rely on it. By following the recommended mitigation steps and always staying informed about the latest security updates, developers can protect their applications and systems from this kind of vulnerability.

Timeline

Published on: 01/10/2022 14:12:00 UTC
Last modified on: 04/22/2022 16:21:00 UTC