CVE-2011-4136 in django
Summary
by MITRE
django.contrib.sessions in Django before 1.2.7 and 1.3.x before 1.3.1, when session data is stored in the cache, uses the root namespace for both session identifiers and application-data keys, which allows remote attackers to modify a session by triggering use of a key that is equal to that session s identifier.
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Analysis
by VulDB Data Team • 11/24/2021
The vulnerability described in CVE-2011-4136 represents a critical session management flaw in the Django web framework that affects versions prior to 1.2.7 and 1.3.1. This issue specifically impacts applications that utilize Django's caching backend for session storage, creating a namespace collision that enables attackers to manipulate user sessions through carefully crafted cache key collisions. The vulnerability stems from the improper handling of cache key namespaces where both session identifiers and application data keys are stored within the same root namespace, fundamentally undermining the security isolation that should exist between different session components.
The technical flaw manifests when Django applications store session data in cache backends such as memcached or redis, which rely on flat key-value storage systems. In the affected versions, session identifiers and application data keys share the same namespace prefix, creating a scenario where an attacker can craft a cache key that exactly matches a legitimate session identifier. This collision allows the attacker to overwrite or manipulate session data by simply triggering cache operations that use the conflicting key name. The vulnerability operates at the cache layer rather than the application layer, making it particularly insidious as it bypasses traditional session validation mechanisms and can be exploited without direct authentication.
From an operational impact perspective, this vulnerability enables a wide range of malicious activities including session hijacking, privilege escalation, and unauthorized access to user accounts. An attacker could potentially modify session data to gain administrative privileges, access restricted resources, or impersonate legitimate users within the application. The vulnerability is particularly dangerous in environments where session data contains sensitive information such as user roles, permissions, or authentication tokens. The attack vector is relatively simple to execute, requiring only knowledge of the session management structure and the ability to trigger cache operations with specific key names, making it a significant risk for applications handling sensitive user data.
The vulnerability maps directly to CWE-200, which covers "Information Exposure," and CWE-284, addressing "Improper Access Control," while also aligning with ATT&CK techniques related to credential access and privilege escalation. Organizations should immediately upgrade to Django versions 1.2.7 or 1.3.1 and later to resolve this issue, as these releases implement proper namespace separation between session identifiers and application data keys. Additional mitigations include implementing proper cache key generation strategies, using unique prefixes for different data types within cache systems, and conducting regular security audits of session management components. The fix typically involves modifying the cache key generation algorithm to ensure that session identifiers and application data keys are stored in separate namespaces, thereby preventing the collision that enables this attack vector.