Algorithmic Complexity Vulnerability in Django
Summary
CVE-2009-3695: Algorithmic complexity vulnerability in the forms library in Django 1.0 before 1.0.4 and 1.1 before 1.1.1 allows remote attackers to cause a denial of service (CPU consumption) via a crafted (1) EmailField (email address... Affects python-django versions < 1.1.1-1. Fixed in 1.1.1-1. How to fix ↓
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Background
Django is a popular web framework for building web applications using the Python programming language. It provides a set of tools and libraries that simplify the development process. The vulnerability in question affects Django versions 1.0 before 1.0.4 and 1.1 before 1.1.1. This vulnerability specifically targets the forms library in Django, which is responsible for handling form input and validation. The forms library includes fields such as EmailField and URLField, which are used to validate email addresses and URLs respectively.
Vulnerability Detail
The vulnerability, identified as CVE-2009-3695, is an algorithmic complexity vulnerability. It allows remote attackers to cause a denial of service (CPU consumption) by exploiting crafted input in the EmailField or URLField. The vulnerability triggers a large amount of backtracking in a regular expression, leading to excessive CPU usage. This can result in a significant degradation of performance or even a complete denial of service if the system becomes overwhelmed.
How To Fix
Minimum fixed version
1.1.1-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade python-djangoTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If upgrading Django is not immediately feasible, a temporary workaround can be implemented. This involves modifying the regular expression used by the affected fields to limit the potential for backtracking. However, it is important to note that this workaround may not provide complete protection and upgrading to the latest version is still the recommended solution. Here is an example of how the regular expression for the EmailField can be modified:
from django.core.validators import EmailValidator
class FixedEmailValidator(EmailValidator):
def __call__(self, value):
self.validate(value)
EmailField.validators.append(FixedEmailValidator())
This code snippet extends the EmailValidator class and overrides its call method to prevent excessive backtracking.
Conclusion
The algorithmic complexity vulnerability in Django's forms library can be exploited to cause a denial of service. Upgrading to Django version 1.1.1 or later is the recommended solution to fix this vulnerability. If immediate upgrade is not possible, a temporary workaround can be implemented. It is important to stay vigilant and apply the necessary fixes to ensure the security and stability of Django applications. For further support on vulnerability remediation, you can reach out to DevNack.com.
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FAQ
The vulnerability can lead to a denial of service (CPU consumption) if exploited. This can result in degraded performance or even a complete system outage.
Django versions 1.0 before 1.0.4 and 1.1 before 1.1.1 are affected by this vulnerability.
You can use the Vulert Playground at Vulert Scanner to check if your Django installation is affected by this vulnerability. Simply upload your package-lock.json file and the playground will analyze it for vulnerabilities.
Yes, a patch is available in Django version 1.1.1 and later. It is recommended to upgrade to the latest version to fix the vulnerability.
There are no known exploits for this vulnerability at the moment. However, it is important to apply the patch or workaround as soon as possible to prevent potential attacks.
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