CVE-2025-3634 is a security vulnerability identified in Moodle versions 4.3.0, 4.4.0, and 4.5.0, which are widely used open-source learning management systems (LMS). The vulnerability stems from improper authentication controls that allow users, specifically students, to enroll themselves in courses prematurely. This bypass occurs because the system fails to enforce completion of mandatory safety checks, notably two-step verification processes, before permitting course enrollment. Essentially, the flaw permits users to circumvent multi-factor authentication (MFA) requirements designed to secure course access. The vulnerability does not require advanced exploitation techniques or elevated privileges beyond a standard user account, making it relatively easy to exploit. Although no known exploits are currently active in the wild, the flaw poses a risk of unauthorized access to course materials and potentially sensitive educational content. The improper authentication mechanism undermines the integrity of the enrollment process, potentially allowing unauthorized users to gain access to restricted courses, which could lead to data leakage or disruption of academic workflows. Since Moodle is often integrated with institutional identity management and access control systems, this vulnerability could also have cascading effects on broader organizational security if exploited.

For European organizations, particularly educational institutions and universities that rely heavily on Moodle for course management and delivery, this vulnerability could lead to unauthorized access to course content and student data. The premature enrollment of unauthorized users could compromise the confidentiality of educational materials and personal information of students and staff. Furthermore, it could disrupt academic integrity by allowing users to access courses without fulfilling prerequisite security steps, potentially enabling cheating or unauthorized participation. The integrity of the learning environment is at risk, as unauthorized users might manipulate course participation records or access exams and assignments prematurely. Additionally, organizations may face reputational damage and compliance issues, especially under the GDPR framework, if personal data is exposed due to exploitation of this vulnerability. The lack of known active exploits reduces immediate risk, but the ease of exploitation and the widespread use of affected Moodle versions in Europe mean that the threat remains significant if left unpatched.

European organizations should immediately verify the Moodle versions deployed and prioritize upgrading to patched versions once available. In the absence of official patches, administrators should implement compensating controls such as temporarily disabling self-enrollment features or enforcing stricter enrollment approval workflows requiring manual validation by course administrators. Additionally, organizations should audit current enrollment logs to detect any suspicious premature enrollments and monitor authentication logs for anomalies related to two-step verification bypass attempts. Enhancing network segmentation to isolate Moodle servers and applying strict access controls can limit the impact of potential exploitation. Institutions should also communicate with users to reinforce the importance of completing two-step verification and consider deploying additional authentication layers at the network or application gateway level. Finally, integrating Moodle with centralized identity providers that enforce MFA at the authentication stage can provide an extra security layer to mitigate this vulnerability.