CVE-2015-0220: Cross-Site Scripting (XSS) in Django

Background

Django is a popular Python web framework that provides a set of tools and libraries for building web applications. It offers features such as URL routing, template rendering, and database management. The vulnerability identified as CVE-2015-0220 affects versions of Django prior to 1.4.18, 1.6.x prior to 1.6.10, and 1.7.x prior to 1.7.3. This vulnerability specifically targets the django.util.http.is_safe_url function, which is responsible for handling redirect URLs. The function fails to properly handle leading whitespaces, allowing remote attackers to exploit this flaw and conduct cross-site scripting (XSS) attacks by crafting malicious URLs.

Vulnerability Detail

The vulnerability arises from the inadequate handling of leading whitespaces in the django.util.http.is_safe_url function. By injecting a crafted URL with a "\njavascript:" prefix, an attacker can execute arbitrary JavaScript code in the context of a victim's browser. This can lead to various security risks, including session hijacking, data theft, and unauthorized actions on behalf of the victim. It is important to note that this vulnerability is specific to redirect URLs and can be exploited by tricking users into clicking on malicious links.

pip install --upgrade "django==6.1.2"

Workaround

If upgrading Django is not immediately feasible, a temporary workaround can be implemented by manually validating and sanitizing redirect URLs. Developers can use functions like Django's url_has_allowed_host_and_scheme to ensure that the URL is safe before performing the redirect. Here is an example of how to use this function:

from django.utils.http import url_has_allowed_host_and_scheme

url = request.GET.get('next', '')
if url_has_allowed_host_and_scheme(url, allowed_hosts=None):
    # Perform the redirect
else:
    # Handle the invalid URL

By explicitly checking the URL's host and scheme, developers can mitigate the risk of XSS attacks.

Conclusion

The vulnerability identified as CVE-2015-0220 in Django versions prior to 1.4.18, 1.6.x prior to 1.6.10, and 1.7.x prior to 1.7.3 allows remote attackers to conduct cross-site scripting (XSS) attacks by exploiting the inadequate handling of leading whitespaces in the django.util.http.is_safe_url function. To mitigate this vulnerability, it is crucial to upgrade Django to the patched versions or implement the provided workaround. For further support on vulnerability remediation, please contact DevNack.com.

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