CVE-2015-5143 in Django
Summary
by MITRE
The session backends in Django before 1.4.21, 1.5.x through 1.6.x, 1.7.x before 1.7.9, and 1.8.x before 1.8.3 allows remote attackers to cause a denial of service (session store consumption) via multiple requests with unique session keys.
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Analysis
by VulDB Data Team • 05/24/2022
The vulnerability identified as CVE-2015-5143 represents a significant denial of service weakness in the Django web framework's session management system. This flaw affects multiple versions of Django including 1.4.21, 1.5.x through 1.6.x, 1.7.x before 1.7.9, and 1.8.x before 1.8.3, creating a persistent security risk for applications relying on Django's session handling mechanisms. The vulnerability stems from insufficient validation and management of session keys within Django's session backends, which are critical components responsible for maintaining user session state across HTTP requests. This weakness specifically targets how Django processes and stores session data when multiple requests are made with distinct session identifiers.
The technical implementation of this vulnerability allows remote attackers to exploit the session storage mechanism by submitting numerous requests containing unique session keys. Each request with a novel session identifier triggers Django's session backend to create and store a new session entry in the configured storage system. This behavior leads to exponential growth in session storage consumption, as the system continuously allocates resources for each unique session key without proper cleanup or rate limiting mechanisms. The flaw operates at the application layer and leverages the fundamental session management architecture of Django, making it particularly dangerous as it can be exploited through normal web traffic patterns without requiring special privileges or advanced attack techniques. The vulnerability is classified as a denial of service condition because it consumes system resources in a manner that can exhaust available storage capacity or memory resources, ultimately rendering the application unavailable to legitimate users.
The operational impact of CVE-2015-5143 extends beyond simple service disruption to potentially compromise system stability and availability. When exploited, this vulnerability can cause significant resource exhaustion in session storage systems, leading to application crashes, performance degradation, or complete service unavailability. The attack is particularly effective against applications using file-based or database-based session storage backends, where the accumulation of session entries can quickly fill disk space or overwhelm database connections. This vulnerability directly violates the principle of resource management in secure application design and can be classified under CWE-400, which addresses unchecked resource consumption. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the denial of service category, specifically targeting application availability through resource exhaustion.
Organizations affected by this vulnerability should immediately implement mitigation strategies including upgrading to patched versions of Django where available, implementing rate limiting on session key generation, and configuring appropriate session storage cleanup mechanisms. The recommended approach involves applying the official Django security patches released for each affected version, as these updates contain fixes for the session key validation and storage mechanisms. Additionally, system administrators should consider implementing monitoring solutions to detect unusual session storage consumption patterns and establish automated alerting for potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper resource management in web applications and demonstrates how seemingly minor flaws in session handling can result in significant operational impacts. Security teams should also review their session storage configurations to ensure adequate capacity planning and implement defensive measures such as session key rotation policies and storage cleanup routines to prevent exploitation of similar vulnerabilities in the future.