In this long read post, we will take an in-depth look at a newly discovered security vulnerability in Django that presents a potential risk for users of certain versions of the popular web development framework. The vulnerability, assigned as CVE-2024-24680, specifically affects the intcomma template filter in Django 3.2 before 3.2.24, 4.2 before 4.2.10, and Django 5. before 5..2. This vulnerability can lead to a denial-of-service (DoS) attack if the filter is used with very long strings.

The Vulnerability: CVE-2024-24680

The intcomma template filter in Django is a simple yet useful tool for developers to quickly format integers with comma separators. However, due to the way this filter is implemented, it becomes vulnerable to a potential DoS attack when used with very long strings. An attacker can exploit this vulnerability to overwhelm the target server's resources by passing in a specially-crafted string that causes excessive CPU usage, leading to the server's unresponsiveness.

Here is an example of the intcomma template filter in use

from django import template
from django.utils import formats

register = template.Library()

@register.filter
def intcomma(value, use_l10n=True):
    # Convert value to get rid of decimal
    value = int(value)
    # Format the integer value with commas as separators
    return formats.number_format(value, , use_l10n)

This simple example shows the intcomma template filter registering itself with the Django template library and then using the number_format function from Django's formats module to format a given integer value by adding commas as separators. Though the filter is helpful and works as intended, it does not account for the fact that very long strings can significantly impact server performance.

A Real-Life Example - Exploiting the Vulnerability

An attacker exploiting this vulnerability could, for example, send an HTTP request containing a crafted string payload such as '9' * 100000 to a server using an application that utilizes the intcomma filter in its templates. The server would then have to process a CPU-intensive task while formatting this string, resulting in high resource usage and potentially causing the server to become unresponsive – a typical DoS attack.

Original References and Official Advisories

This vulnerability was publicly disclosed and tracked with the CVE identifier CVE-2024-24680. The official advisories and references for this vulnerability include:

- NVD - CVE-2024-24680
- Django Security Advisory
- Django GitHub Commit Fixing the Issue

The Fix and Mitigation Steps

The Django project quickly addressed this vulnerability by releasing security updates for the affected versions. The updates include the following patched versions:

Django 5..2

Users of Django impacted by this vulnerability should upgrade their installations as soon as possible to mitigate any potential threats:

pip install --upgrade 'Django>=3.2.24,<3.3'
pip install --upgrade 'Django>=4.2.10,<4.3'
pip install --upgrade 'Django>=5..2,<5.1'

In conclusion, the CVE-2024-24680 vulnerability is a crucial security issue that affects the popular web development framework Django. With this vulnerability, attackers can potentially exploit applications that use the intcomma template filter with very long strings, leading to a denial-of-service attack. Users of Django, specifically versions 3.2, 4.2, and 5., should upgrade their installations immediately to the patched versions to prevent potential issues.

Timeline

Published on: 02/06/2024 22:16:15 UTC
Last modified on: 04/20/2024 03:15:06 UTC