CVE-2015-3982 in Django
Summary
by MITRE
The session.flush function in the cached_db backend in Django 1.8.x before 1.8.2 does not properly flush the session, which allows remote attackers to hijack user sessions via an empty string in the session key.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2015-3982 affects Django web applications running version 1.8.x before 1.8.2, specifically within the cached_db backend implementation. This issue resides in the session management functionality where the session.flush method fails to properly clear session data when processing certain session keys. The flaw creates a critical security gap that enables remote attackers to exploit session hijacking techniques by manipulating session keys with empty string values. The vulnerability stems from inadequate input validation and session key handling within the caching backend subsystem, which is commonly used in Django applications for session storage and retrieval.
The technical implementation of this vulnerability demonstrates a classic case of improper session key validation within the cached database backend. When the session.flush function processes a session key that contains an empty string, the function fails to properly invalidate or clear the associated session data from the cache storage. This occurs because the system does not adequately check for or handle empty session keys during the flush operation, allowing stale session data to persist in memory or cache storage. The flaw specifically manifests when an attacker can submit or manipulate a session key that resolves to an empty string, which then bypasses normal session cleanup procedures and maintains access to potentially compromised session information.
From an operational impact perspective, this vulnerability creates significant risk for Django applications that rely on the cached_db session backend. Attackers can leverage this weakness to maintain unauthorized access to user sessions by exploiting the improper session flushing behavior. The vulnerability essentially allows for session hijacking where an attacker can reuse or manipulate session data that should have been properly cleared, potentially gaining access to user accounts, sensitive data, or privileged operations within the application. The attack vector is particularly concerning because it requires minimal privileges and can be executed remotely, making it an attractive target for malicious actors seeking to compromise user sessions.
Security practitioners should address this vulnerability by upgrading to Django version 1.8.2 or later, which includes the necessary patches to properly handle session key validation and flushing operations. The fix implemented in the patched version ensures that empty session keys are properly identified and handled during the flush process, preventing the persistence of stale session data. Organizations should also review their session management configurations and consider implementing additional security measures such as session key randomization, proper session timeout configurations, and monitoring for unusual session access patterns. This vulnerability aligns with CWE-20, which covers "Improper Input Validation," and relates to ATT&CK technique T1548.001 for "Abuse Elevation Control Mechanism" through session hijacking. Additionally, the issue demonstrates characteristics of improper session handling that could potentially map to ATT&CK technique T1133 for "External Remote Services" when attackers exploit session management weaknesses to maintain persistent access to systems.