CVE-2015-0222 in Django
Summary
by MITRE
ModelMultipleChoiceField in Django 1.6.x before 1.6.10 and 1.7.x before 1.7.3, when show_hidden_initial is set to True, allows remote attackers to cause a denial of service by submitting duplicate values, which triggers a large number of SQL queries.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability CVE-2015-0222 represents a significant denial of service weakness in the Django web framework that affects versions prior to 1.6.10 and 1.7.3. This flaw specifically targets the ModelMultipleChoiceField component within Django's forms system, which is commonly used for handling multiple selection inputs in web applications. The vulnerability becomes exploitable when the show_hidden_initial parameter is enabled, creating a condition where malicious actors can manipulate form submissions to trigger excessive database operations.
The technical mechanism behind this vulnerability stems from how Django processes multiple choice fields when hidden initial values are displayed. When show_hidden_initial=True is configured, Django must validate and process the initial state of multiple choice selections, which involves complex database queries to ensure data consistency. The flaw occurs because the framework does not properly handle duplicate values in the submitted data, leading to a quadratic complexity issue where each duplicate value triggers additional database lookups. This creates a scenario where a single malicious request can generate hundreds or thousands of SQL queries, overwhelming database resources and consuming system memory.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can effectively disable web applications through denial of service attacks. Attackers can craft specially formatted requests containing numerous duplicate values to cause the application server to spend excessive time processing database queries rather than serving legitimate requests. This behavior aligns with the CWE-400 weakness category, which encompasses resource exhaustion vulnerabilities that can be exploited to deny service to legitimate users. The vulnerability particularly affects applications that rely heavily on Django forms with multiple choice fields, making it a critical concern for web applications handling user input through complex selection interfaces.
Security practitioners should note that this vulnerability demonstrates the importance of proper input validation and query optimization in web frameworks. The attack vector requires minimal privileges and can be executed through standard web requests, making it particularly dangerous in production environments. Organizations using affected Django versions should prioritize immediate patching to prevent exploitation, as the vulnerability does not require authentication or specialized tools for successful exploitation. The remediation process involves upgrading to Django versions 1.6.10 or 1.7.3, which include fixes that properly handle duplicate values in ModelMultipleChoiceField operations. Additionally, implementing request rate limiting and input sanitization measures can provide additional defense-in-depth protection against similar vulnerabilities that may exist in other components of the application stack. This vulnerability also highlights the relevance of the ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, as the malicious behavior directly targets database resources to achieve service disruption.