CVE-2020-25701 in Moodle
Summary
by MITRE • 11/19/2020
If the upload course tool in Moodle was used to delete an enrollment method which did not exist or was not already enabled, the tool would erroneously enable that enrollment method. This could lead to unintended users gaining access to the course. Versions affected: 3.9 to 3.9.2, 3.8 to 3.8.5, 3.7 to 3.7.8, 3.5 to 3.5.14 and earlier unsupported versions. This is fixed in moodle 3.9.3, 3.8.6, 3.7.9, 3.5.15, and 3.10.
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Analysis
by VulDB Data Team • 12/09/2020
The vulnerability described in CVE-2020-25701 represents a critical access control flaw within Moodle's course management system that directly impacts the integrity of user enrollment mechanisms. This issue specifically affects the upload course tool functionality where administrators attempt to delete enrollment methods from courses. The flaw manifests when the system processes deletion requests for enrollment methods that either do not exist within the course configuration or are not currently enabled. The erroneous behavior occurs because the system fails to properly validate the existence and enabled status of enrollment methods before executing modification operations. This misconfiguration creates a logical error in the system's conditional logic, leading to unintended consequences when processing these specific deletion requests.
The technical nature of this vulnerability can be categorized under CWE-284, which addresses improper access control, and more specifically relates to CWE-285, which deals with improper authorization. The flaw operates at the application logic level where the system's validation checks are insufficient to prevent unauthorized modifications to enrollment configurations. When an administrator attempts to delete a non-existent or non-enabled enrollment method through the upload tool, the system incorrectly interprets this action as a request to enable the method instead of properly rejecting the invalid operation. This misinterpretation stems from flawed input validation and insufficient state checking within the enrollment management module, creating a scenario where the system's behavior contradicts the user's intended action.
The operational impact of this vulnerability is severe as it directly compromises the security posture of Moodle installations by potentially granting unauthorized access to course materials. An attacker or malicious administrator could exploit this flaw to enable enrollment methods that were previously disabled or non-existent, thereby allowing users who should not have access to gain entry to restricted course content. This vulnerability affects multiple Moodle versions including the most recent stable releases, making it particularly concerning for organizations that have not yet updated their systems. The risk is amplified because the vulnerability occurs during routine administrative operations, making it difficult to detect and potentially allowing attackers to remain undetected while expanding their access privileges.
Organizations affected by this vulnerability should immediately implement the mitigations provided in the patched versions of Moodle, specifically upgrading to versions 3.9.3, 3.8.6, 3.7.9, 3.5.15, and 3.10. The patch addresses the core logic error by implementing proper validation checks that ensure enrollment methods are properly verified before any modification operations are executed. System administrators should also review existing enrollment configurations to identify any potentially enabled methods that may have been inadvertently activated through exploitation of this vulnerability. Additionally, implementing monitoring of administrative actions and enrollment method changes can provide early detection of unauthorized modifications to course access controls. The vulnerability highlights the importance of proper input validation and state management in security-critical applications, particularly in educational platforms where access control directly impacts data privacy and security compliance requirements.