CVE-2016-6337 in MediaWiki
Summary
by MITRE
MediaWiki 1.27.x before 1.27.1 might allow remote attackers to bypass intended session access restrictions by leveraging a call to the UserGetRights function after Session::getAllowedUserRights.
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability identified as CVE-2016-6337 affects MediaWiki versions 1.27.x prior to 1.27.1 and represents a critical session management flaw that undermines access control mechanisms. This issue stems from a misconfiguration in how the MediaWiki platform handles user rights validation during session processing, creating a potential bypass of intended security restrictions. The vulnerability specifically manifests when the UserGetRights function is invoked after Session::getAllowedUserRights, allowing malicious actors to exploit the timing and sequence of these function calls to gain unauthorized access to restricted resources.
The technical root cause of this vulnerability lies in the improper handling of user permission checks within MediaWiki's session management framework. When a user session is established, the system should consistently enforce access controls based on the user's assigned rights and privileges. However, in the affected versions, the sequence of operations allows for a window where the UserGetRights function can return cached or stale permission data that does not reflect the current session's actual access restrictions. This creates an inconsistency between what the system believes the user can access versus what the session actually permits, enabling attackers to leverage this discrepancy for privilege escalation.
From an operational impact perspective, this vulnerability poses significant risks to MediaWiki installations that rely on role-based access control for their content management systems. Attackers who successfully exploit this flaw could potentially access restricted pages, edit protected content, or perform administrative functions without proper authorization. The vulnerability is particularly concerning because it operates at the session level rather than requiring direct code execution or authentication bypass, making it more difficult to detect and prevent through traditional security measures. Organizations running MediaWiki instances with sensitive content or administrative controls would be especially vulnerable to this type of unauthorized access.
The flaw aligns with CWE-284, which addresses improper access control issues, and demonstrates characteristics consistent with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting. Organizations should immediately apply the patch released in MediaWiki 1.27.1 to address this vulnerability, as it represents a fundamental breakdown in the platform's session management security model. Additionally, administrators should review their current session handling configurations and implement monitoring for anomalous access patterns that might indicate exploitation attempts. The vulnerability underscores the importance of proper function call sequencing and access control validation in web application security, particularly in content management systems where user permissions directly control system access.