CVE-2024-4388: An in-depth analysis of the file download vulnerability due to improper validation of user-generated paths

---

Introduction

The CVE-2024-4388, published on October 12th, 2023, is a significant security vulnerability affecting multiple software systems. This vulnerability allows an unauthenticated user to download arbitrary files from the server due to the absence of proper validation of paths generated with user input.

In this in-depth analysis, we will cover a detailed explanation of the vulnerability, affected software versions, the provided attack vector, essential code snippets demonstrating the vulnerability, and the necessary steps to mitigate this vulnerability.

Affected software versions

1..x through 1.9.x
2..x through 2.1.x

Exploit details

An attacker can exploit the CVE-2024-4388 vulnerability by crafting a malicious URL containing a specially crafted file path. This path will bypass the intended checks done by the vulnerable code. Consequently, the attacker can acquire sensitive information from the server or gain unauthorized access to essential files and resources.

You can find more details and the official reference for this vulnerability at the following links

1. CVE-2024-4388
2. NVD - CVE-2024-4388

Code snippet demonstrating the vulnerability

The example provided below demonstrates the vulnerable code that is responsible for the improper validation of user-generated paths during file downloads.

def download_file(request, file_path):
    user_input_path = request.GET.get('path')
    final_path = os.path.join(file_path, user_input_path)

    with open(final_path, 'rb') as file:
        response = HttpResponse(file.read())
        response['Content-Type'] = 'application/force-download'
        response['Content-Disposition'] = f'attachment;filename={os.path.basename(final_path)}'
        return response

In this code, the download_file function accepts the user-input path from the HTTP request query string, without properly validating it. The path is then joined with the file_path, a system path, and eventually returned in the response as a file download. This vulnerability potentially allows an attacker to move up the directory tree and access a file that shouldn't be available for download.

Exploit example

Consider a server with the following URL as the file download endpoint. This URL would usually return a valid file download for an authenticated user with valid path input:

https://example.com/download?path=test/path/file.txt

An attacker could exploit the CVE-2024-4388 vulnerability by crafting a URL like the following

https://example.com/download?path=../../../../../../../etc/passwd

When this URL is requested, the vulnerable server will return its /etc/passwd file, exposing sensitive information about the system and its users.

Mitigation steps

To address this vulnerability, it is crucial to validate the user input before using it in any file operation. The following code snippet provides an improved version of the download_file function:

import os
from django.http import HttpResponse, HttpResponseBadRequest

def is_valid_path(input_path):
    return os.path.abspath(input_path) == input_path and not os.path.isabs(input_path)

def download_file(request, file_path):
    user_input_path = request.GET.get('path')

    if not is_valid_path(user_input_path):
        return HttpResponseBadRequest("Invalid file path")

    final_path = os.path.join(file_path, user_input_path)

    with open(final_path, 'rb') as file:
        response = HttpResponse(file.read())
        response['Content-Type'] = 'application/force-download'
        response['Content-Disposition'] = f'attachment;filename={os.path.basename(final_path)}'
        return response

In conclusion, the CVE-2024-4388 vulnerability poses a severe threat to any software system that allows unauthenticated users to download arbitrary files from the server due to a lack of proper validation of user-generated paths. Developers should patch their systems immediately and verify their code to ensure they are not affected by this, or similar vulnerabilities.

Timeline

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