CVE-2018-1082 in Moodle
Summary
by MITRE
A flaw was found in Moodle 3.4 to 3.4.1, and 3.3 to 3.3.4. If a user account using OAuth2 authentication method was once confirmed but later suspended, the user could still login to the site.
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Analysis
by VulDB Data Team • 01/22/2020
This vulnerability exists in Moodle versions 3.4.0 through 3.4.1 and 3.3.0 through 3.3.4, representing a critical authentication bypass flaw that undermines the platform's user access control mechanisms. The issue specifically affects users who authenticate through the OAuth2 method, where the system fails to properly validate account status during the authentication process. When a user account that previously used OAuth2 authentication was confirmed and subsequently suspended by administrators, the vulnerability allows the suspended user to continue accessing the system through the OAuth2 login mechanism, effectively bypassing the intended account suspension.
The technical root cause of this vulnerability lies in the improper implementation of account status validation within the OAuth2 authentication flow. During the OAuth2 login process, the system should verify that the user account is active and not suspended before granting access, but this validation step is either missing or inadequately implemented. This flaw demonstrates a clear breakdown in the principle of least privilege and proper access control enforcement, where suspended users retain access to system resources despite explicit administrative actions to revoke their privileges. The vulnerability is classified as a weakness in authentication mechanisms and falls under the broader category of access control vulnerabilities that can lead to unauthorized system access.
The operational impact of this vulnerability is significant as it allows suspended users to maintain access to Moodle courses, resources, and potentially sensitive information. This creates a persistent security risk where administrators cannot rely on account suspension as an effective access control measure. Attackers could exploit this vulnerability by targeting suspended accounts that still have valid OAuth2 tokens or by creating new suspended accounts to maintain unauthorized access. The flaw particularly affects educational institutions and organizations that rely on Moodle for learning management, as it compromises the integrity of user access controls and potentially exposes confidential student or administrative data to unauthorized individuals.
Organizations should immediately update their Moodle installations to versions 3.3.5, 3.4.2, or later to remediate this vulnerability, as these releases contain the necessary patches to properly validate account status during OAuth2 authentication. Additionally, administrators should review their OAuth2 configuration settings and ensure that account suspension policies are properly enforced across all authentication methods. The vulnerability aligns with attack patterns documented in the attack tree model where authentication bypasses are categorized as critical threats to system integrity, and it represents a failure to implement proper account lifecycle management. Security teams should also consider implementing additional monitoring to detect suspicious login activities from previously suspended accounts and establish regular audits of user access controls to identify potential unauthorized access scenarios.