CVE-2021-44858 in MediaWiki
Summary
by MITRE • 12/20/2021
An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1. It is possible to use action=edit&undo= followed by action=mcrundo and action=mcrrestore to view private pages on a private wiki that has at least one page set in $wgWhitelistRead.
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Analysis
by VulDB Data Team • 12/24/2021
The vulnerability identified as CVE-2021-44858 represents a critical access control flaw within the MediaWiki content management system that affects multiple versions including 1.35.5, 1.36.3, and 1.37.1. This security issue stems from improper handling of page access permissions when utilizing specific API endpoints, particularly those related to editing and undo functionality. The flaw allows authenticated users to bypass intended access restrictions and view private content on wikis that implement page-level read whitelisting through the $wgWhitelistRead configuration parameter. The vulnerability manifests when attackers exploit the interaction between action=edit&undo parameters and subsequent action=mcrundo and action=mcrrestore operations, creating a pathway to access restricted information that should only be visible to authorized users with appropriate permissions.
The technical implementation of this vulnerability leverages MediaWiki's internal page revision management system and undo functionality. When users perform an edit operation followed by undo actions, the system maintains references to page revisions in memory. The flaw occurs because the undo and restore operations do not properly validate whether the requesting user has appropriate permissions to access the specific page content being manipulated. This misconfiguration creates a window where authenticated users can exploit the system's revision handling to access private pages that are normally restricted. The vulnerability is particularly concerning because it operates within the legitimate API endpoints designed for content management, making detection more challenging for security monitoring systems. The issue aligns with CWE-284, which addresses improper access control, and demonstrates how insufficient authorization checks during revision operations can lead to information disclosure.
The operational impact of CVE-2021-44858 extends beyond simple information disclosure, potentially compromising the confidentiality of private wiki content including sensitive documentation, internal communications, and restricted user data. Organizations running MediaWiki installations with $wgWhitelistRead configured are at risk of unauthorized access to private pages, which could include confidential business information, personal user data, or restricted project documentation. The vulnerability affects both public and private wiki deployments where administrators have implemented page-level access controls, making it particularly dangerous for enterprises that rely on MediaWiki for internal knowledge management. Attackers can systematically exploit this vulnerability to enumerate private content, potentially leading to data breaches, intellectual property theft, or compliance violations depending on the nature of the restricted information stored on the wiki platform. The attack vector requires minimal privileges as users only need basic authentication to access the wiki system, making the exploitation accessible to a broad range of threat actors.
Mitigation strategies for CVE-2021-44858 primarily focus on immediate software updates to patched versions of MediaWiki, specifically upgrading to 1.35.5, 1.36.3, or 1.37.1 respectively. Organizations should implement comprehensive patch management procedures to ensure all MediaWiki instances are updated promptly. Additionally, administrators should review and strengthen their access control configurations, particularly when implementing $wgWhitelistRead settings, to ensure proper validation of user permissions during revision operations. Network-level monitoring should be enhanced to detect unusual API access patterns involving undo and restore operations, as these may indicate exploitation attempts. Security teams should also consider implementing additional access controls at the application level, such as rate limiting for API endpoints and enhanced logging of revision-related activities. The vulnerability highlights the importance of thorough testing of access control mechanisms during security reviews, particularly for systems that handle sensitive information. Organizations should conduct regular security assessments of their wiki platforms and implement principle of least privilege configurations to minimize the potential impact of similar vulnerabilities in the future. This case demonstrates the critical nature of maintaining up-to-date security patches and the importance of proper access control implementation in content management systems.