CVE-2011-4137: Django verify_exists URLField Denial of Service Vulnerability
Summary
CVE-2011-4137: Denial of service in django. Affects django across 2 version ranges.
< 1.2.7
>= 1.3, < 1.3.1
Fixed in 1.2.7 or 1.3.1, depending on the release line you run. How to fix ↓
Also tracked for
- python-django · Debian:11
The same CVE-2011-4137 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Django is a popular Python web framework that simplifies the development of web applications. It includes various features and components to handle common web development tasks, such as URL handling using the URLField implementation. However, versions before 1.2.7 and 1.3.x before 1.3.1 are vulnerable to a denial of service (DoS) attack due to the insecure implementation of the verify_exists functionality in the URLField.
Vulnerability Detail
The verify_exists functionality in Django's URLField relies on Python libraries that attempt to access an arbitrary URL without a timeout. This allows remote attackers to exploit the vulnerability in multiple ways:
- Slow response: Attackers can send a request to a URL that responds slowly, causing resource consumption and potentially leading to a DoS condition.
- Completed TCP connection with no application data sent: Attackers can establish a TCP connection to a URL without sending any application data, consuming server resources and potentially causing a DoS condition.
- Large amount of application data: Attackers can send a large amount of application data to a URL, overwhelming the server and causing a DoS condition.
This vulnerability is similar to CVE-2011-1521.
How To Fix
Latest published version: 6.1.2 as of 22 Oct 2026
pip install --upgrade "django==6.1.2"Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 1.2.71.2.7pip install --upgrade "django==1.2.7" -
>= 1.3, < 1.3.11.3.1pip install --upgrade "django==1.3.1"
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Workaround
If upgrading to a fixed version is not immediately possible, a workaround can be implemented by disabling the verify_exists functionality in the URLField. This can be done by setting the 'verify_exists' attribute of the URLField to False. However, it is important to note that this workaround may impact the functionality of the application and should only be considered as a temporary solution until the upgrade can be performed.
Conclusion
The Django verify_exists URLField vulnerability (CVE-2011-4137) can be exploited by remote attackers to cause a denial of service condition. It is recommended to upgrade to a fixed version of Django or apply the provided workaround. For further assistance and support in vulnerability remediation, please contact DevNack.com.
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FAQ
Django is a Python web framework that simplifies web application development by providing various features and components.
The URLField is a field type in Django used for handling URLs. It provides validation and other functionality related to URLs.
This vulnerability can be exploited by remote attackers to cause a denial of service (DoS) condition, potentially leading to resource exhaustion and application downtime.
To fix this vulnerability, it is recommended to upgrade to a fixed version of Django (1.2.7 or 1.3.1). Alternatively, you can disable the verify_exists functionality in the URLField as a temporary workaround.
There are no known public exploits available for this vulnerability at the time of writing. However, it is important to apply the necessary security patches or upgrades to mitigate the risk.
References
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