CVE-2014-7846 in Moodle
Summary
by MITRE
tag/tag_autocomplete.php in Moodle through 2.4.11, 2.5.x before 2.5.9, 2.6.x before 2.6.6, and 2.7.x before 2.7.3 does not consider the moodle/tag:edit capability before adding a tag, which allows remote authenticated users to bypass intended access restrictions via an AJAX request.
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Analysis
by VulDB Data Team • 04/04/2022
The vulnerability identified as CVE-2014-7846 resides within Moodle's tag_autocomplete.php script, affecting versions through 2.4.11, 2.5.x before 2.5.9, 2.6.x before 2.6.6, and 2.7.x before 2.7.3. This represents a critical access control flaw that undermines the platform's security model by allowing authenticated users to bypass intended permissions. The issue specifically targets the moodle/tag:edit capability, which should normally govern who can add or modify tags within the learning management system. The vulnerability manifests through an AJAX request mechanism that fails to properly validate user permissions before executing tag addition operations, creating a path for privilege escalation.
The technical flaw stems from inadequate input validation and permission checking within the tag_autocomplete.php endpoint. When authenticated users make AJAX requests to this script, the system does not verify whether the requesting user possesses the necessary moodle/tag:edit capability before processing tag addition requests. This omission creates a direct bypass of Moodle's intended access control mechanisms, allowing users to add tags to resources they should not be permitted to modify. The vulnerability operates at the application layer and leverages the existing authentication state of legitimate users to perform unauthorized actions, making it particularly dangerous as it exploits trust relationships within the system.
The operational impact of this vulnerability extends beyond simple unauthorized tag addition, as it represents a fundamental breakdown in Moodle's capability-based access control system. Attackers could potentially manipulate course content tags, metadata, or resource categorization in ways that might affect data integrity and user experience. The vulnerability affects the core functionality of Moodle's tagging system, which is used extensively for organizing course materials, resources, and content. Depending on the system configuration, this could lead to information disclosure, data manipulation, or the creation of misleading content tags that might confuse other users or affect search and navigation functionality. The vulnerability's persistence across multiple version lines indicates a systemic issue in the permission validation logic that required coordinated patching efforts.
This vulnerability aligns with CWE-284, which describes improper access control issues where systems fail to properly enforce access restrictions. The flaw also maps to ATT&CK technique T1078.004, which covers valid accounts with elevated privileges, as the vulnerability allows authenticated users to perform actions beyond their intended permissions without requiring additional privilege escalation techniques. Organizations using affected Moodle versions face significant risk of unauthorized content modification, potential data integrity issues, and compromised user trust in the platform's security mechanisms. The vulnerability's presence across multiple release branches demonstrates the importance of proper capability validation in web applications and highlights the need for comprehensive security testing of AJAX endpoints that handle user-modifiable content.
Mitigation strategies for CVE-2014-7846 require immediate implementation of patches provided by Moodle developers for all affected versions. System administrators should ensure that all instances of Moodle are updated to versions that include the necessary permission validation fixes. Additionally, organizations should conduct thorough security assessments of their Moodle installations to verify that no unauthorized tag modifications have occurred. Network monitoring should be enhanced to detect unusual AJAX request patterns that might indicate exploitation attempts. The vulnerability underscores the importance of implementing proper input validation and capability checks for all user-facing AJAX endpoints, particularly those that modify system state or content. Regular security audits and vulnerability scanning should be performed to identify similar access control weaknesses in other components of the learning management system.