CVE-2015-5963 in Django
Summary
by MITRE
contrib.sessions.middleware.SessionMiddleware in Django 1.8.x before 1.8.4, 1.7.x before 1.7.10, 1.4.x before 1.4.22, and possibly other versions allows remote attackers to cause a denial of service (session store consumption or session record removal) via a large number of requests to contrib.auth.views.logout, which triggers the creation of an empty session record.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/12/2022
The vulnerability identified as CVE-2015-5963 represents a significant denial of service weakness within the Django web framework's session management system. This flaw exists in multiple versions of Django including 1.8.x before 1.8.4, 1.7.x before 1.7.10, and 1.4.x before 1.4.22, making it a widespread issue affecting numerous applications built on this popular Python web framework. The vulnerability specifically targets the SessionMiddleware component which is responsible for managing user sessions in Django applications, creating a critical point of failure that adversaries can exploit to disrupt service availability.
The technical mechanism behind this vulnerability involves the improper handling of logout requests within Django's authentication system. When a large number of requests are made to contrib.auth.views.logout, the SessionMiddleware creates empty session records in the session store without proper validation or rate limiting. This behavior stems from the middleware's design flaw where it does not adequately check whether a session record already exists or whether the logout operation should be processed with the same session identifier. The empty session records consume storage space in the session backend and can lead to session store exhaustion, particularly when attackers generate thousands or millions of concurrent logout requests.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire application infrastructure. Attackers can leverage this weakness to consume all available session storage space, effectively preventing legitimate users from creating new sessions or accessing authenticated portions of the application. This denial of service attack can be executed with minimal resources and can quickly overwhelm session stores in applications with limited storage capacity. The vulnerability particularly affects applications that rely heavily on session-based authentication and have session backends with limited capacity such as database sessions or file-based session storage.
This vulnerability maps directly to CWE-400, which describes "Uncontrolled Resource Consumption" and specifically relates to the improper handling of session records in web applications. The attack pattern aligns with ATT&CK technique T1499.004, "Endpoint Denial of Service," where adversaries target application resources to prevent legitimate users from accessing services. The flaw demonstrates poor input validation and resource management practices that are common in web application security vulnerabilities. Organizations running affected Django versions face significant risk as this vulnerability can be exploited through automated tools that generate massive volumes of logout requests, potentially causing cascading failures in applications that depend on session management for user authentication and authorization.
Mitigation strategies for CVE-2015-5963 require immediate patching of affected Django versions to the latest available releases including 1.8.4, 1.7.10, and 1.4.22 respectively. Organizations should also implement rate limiting mechanisms at the application level to restrict the number of logout requests per user or IP address within a given time period. Additional protective measures include configuring session backends with appropriate capacity limits and monitoring session store consumption patterns to detect anomalous usage. Network-level firewalls and web application firewalls can be configured to identify and block suspicious logout request patterns. Security teams should also implement proper logging and alerting for session management activities to quickly identify potential exploitation attempts and maintain audit trails for forensic analysis.