CVE-2017-12794 in Django
Summary
by MITRE
In Django 1.10.x before 1.10.8 and 1.11.x before 1.11.5, HTML autoescaping was disabled in a portion of the template for the technical 500 debug page. Given the right circumstances, this allowed a cross-site scripting attack. This vulnerability shouldn't affect most production sites since you shouldn't run with "DEBUG = True" (which makes this page accessible) in your production settings.
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Analysis
by VulDB Data Team • 01/11/2021
The vulnerability identified as CVE-2017-12794 represents a critical cross-site scripting weakness in the Django web framework that emerged from a specific design flaw in the framework's debug error handling mechanism. This vulnerability affected Django versions 1.10.x prior to 1.10.8 and 1.11.x prior to 1.11.5, creating a security risk that could be exploited by malicious actors to inject malicious scripts into web applications. The flaw specifically targeted the technical 500 debug page, which is automatically displayed when Django encounters an unhandled exception during application execution, making it a particularly dangerous issue given the context in which it occurs.
The technical root cause of this vulnerability stems from Django's HTML autoescaping mechanism being inadvertently disabled within a specific portion of the template responsible for rendering the 500 error page. This template, designed to provide detailed debugging information to developers when errors occur, contained a section where user-provided input was not properly sanitized before being rendered in the browser. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a weakness where the application fails to properly escape output that is rendered in the browser context. This particular implementation flaw created a situation where attackers could inject malicious scripts that would execute in the context of users who viewed the debug page, potentially leading to session hijacking, data theft, or other malicious activities.
The operational impact of this vulnerability extends beyond the immediate security risk, as it demonstrates a fundamental failure in how Django handled error reporting in debug mode. While the vulnerability was designed to be accessible only when DEBUG = True was set in the application configuration, which is standard practice for production environments, it created a dangerous scenario where even developers who might have accidentally left debug mode enabled could be exposed to attack vectors. The attack surface was particularly concerning because the 500 error page was designed to display detailed information about the application's internal state, including potentially sensitive data, making it an attractive target for attackers seeking to gain deeper insights into the application architecture. This vulnerability aligns with ATT&CK technique T1211 which involves the exploitation of debug mode functionality to gain unauthorized access to system information.
The mitigation strategy for CVE-2017-12794 required immediate patching of affected Django versions to restore proper HTML escaping in the debug error page template. Organizations needed to ensure that all Django installations were updated to versions 1.10.8 or 1.11.5, respectively, to address the vulnerability. Beyond patching, security teams were advised to review their deployment configurations to ensure that DEBUG = True was never enabled in production environments, as this would eliminate the risk of exploitation entirely. The incident highlighted the importance of proper input validation and output sanitization in web applications, particularly in error handling components where sensitive information might be displayed. Additionally, organizations were encouraged to implement automated security scanning tools that could detect the presence of debug mode in production environments, as this represented a common misconfiguration that could lead to similar vulnerabilities in other frameworks or applications. The vulnerability underscored the critical need for security awareness training for development teams to ensure proper configuration management and the understanding that debug mode should never be enabled in production systems.