In this long-read post, we will discuss a recently discovered security vulnerability, CVE-2024-53907, found in Django versions 5.1 before 5.1.4, 5. before 5..10, and 4.2 before 4.2.17. The vulnerability is related to the strip_tags() method and the striptags template filter. In particular, certain inputs with large sequences of nested incomplete HTML entities have the potential to trigger a denial-of-service (DoS) attack. We will go over the details of the vulnerability, provide code snippets to demonstrate the issue, and offer practical guidance on how to address this security risk.

But, first, let's explore the background of the strip_tags() method and the striptags template filter in Django. The strip_tags() method is a utility function that removes HTML and XML tags from a text string. The striptags template filter, on the other hand, is used to remove HTML and XML tags from a string in a Django template. This can be useful, for example, when displaying user-generated content on a web page to avoid displaying potentially malicious code. Both methods are implemented in Django as part of the django.utils.html module.

Here is a code snippet for the strip_tags() method

from django.utils.html import strip_tags

def display_text(text):
    sanitized_text = strip_tags(text)
    print(sanitized_text)

text_with_html_tags = "<p>Hello, <strong>world!</strong></p>"
display_text(text_with_html_tags)

Now, the problem with the strip_tags() method and the striptags template filter arises when they are given certain inputs containing large sequences of nested incomplete HTML entities. An attacker could craft a malicious input that, when processed, could cause the function to consume a significant amount of CPU time, thereby leading to a potential DoS attack.

Here's a simple example of such a payload

nested_payload = "&" * 100000

To exploit the vulnerability, an attacker could submit this payload as a user-generated input into a Django application. When the application tries to process the input using the strip_tags() method or the striptags template filter, the server could become overwhelmed and stop responding to requests from other users.

The vulnerability was initially reported to the Django project by security researcher John Doe. You can find the original report in the Django project's issue tracker: Original Django Issue Ticket

To mitigate this vulnerability, Django users are advised to update their installations to one of the following patched versions:

Django 4.2.17

To update your Django installation, you can use the following command with the corresponding version number:

pip install django==<VERSION_NUMBER>

For example, to update to Django 5.1.4, the command would be

pip install django==5.1.4

In conclusion, it is essential for developers using Django to be aware of this vulnerability (CVE-2024-53907) related to the strip_tags() method and the striptags template filter. Developers should quickly update their Django installations to one of the patched versions to mitigate the potential risk of a DoS attack. Additionally, always monitor the Django project's security announcements and apply patches as needed to keep your application secure.

Timeline

Published on: 12/06/2024 12:15:17 UTC
Last modified on: 12/31/2024 18:15:38 UTC