CVE-2025-3640 is a medium-severity authorization bypass vulnerability identified in Moodle versions 4.1.0, 4.3.0, 4.4.0, and 4.5.0. Moodle is a widely used open-source learning management system (LMS) deployed globally, including extensively across European educational institutions and organizations. The vulnerability arises due to insufficient capability checks within the application, allowing a user enrolled in a course to access certain personal details of other users in the same course without proper authorization. Specifically, an attacker can retrieve information such as the full name and profile image URL of other users they should not have permission to view. The flaw is triggered through a user-controlled key, which bypasses the intended access control mechanisms. According to the CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N), the vulnerability can be exploited remotely over the network with low attack complexity, requiring the attacker to have legitimate user privileges (enrolled in the course) but no user interaction is needed beyond that. The impact is limited to confidentiality, with no integrity or availability effects. There are no known exploits in the wild at the time of publication, and no patches or vendor advisories are currently linked, indicating that organizations should proactively monitor for updates and apply fixes once available. This vulnerability does not allow privilege escalation or access to sensitive data beyond basic profile information, but it still represents a privacy concern, especially in regulated environments where user data protection is critical.

For European organizations, particularly educational institutions, universities, and corporate training platforms using Moodle, this vulnerability poses a privacy risk by exposing personal user information without consent. While the data exposed is limited to full names and profile image URLs, such information could be aggregated or combined with other data to facilitate social engineering, targeted phishing, or profiling attacks. In the context of the EU's GDPR, unauthorized disclosure of personal data—even seemingly benign profile details—can lead to compliance violations and potential fines. Additionally, the breach of user trust may damage institutional reputations. Since Moodle is widely adopted in Europe, including in public sector education and private enterprises, the scope of affected systems is significant. However, the impact is not critical as it does not affect system integrity or availability, nor does it allow access to more sensitive data such as grades, financial information, or authentication credentials. The requirement for the attacker to be an enrolled user limits the attack surface to insiders or compromised accounts, reducing the likelihood of large-scale exploitation but still necessitating vigilance.

1. Immediate mitigation should focus on restricting course enrollment to verified users and monitoring for unusual access patterns within courses to detect potential abuse. 2. Implement strict role-based access controls and review Moodle configuration settings to ensure that user profile visibility is limited according to privacy policies. 3. Encourage users to limit the amount of personal information displayed in their profiles, such as avoiding uploading sensitive images or unnecessary personal details. 4. Network-level controls such as web application firewalls (WAFs) can be tuned to detect and block anomalous requests attempting to exploit this flaw, especially those that attempt to enumerate user details. 5. Organizations should maintain up-to-date backups and have incident response plans tailored to data privacy incidents. 6. Monitor Moodle security advisories and apply patches promptly once released. 7. Conduct internal audits and penetration tests focusing on authorization mechanisms within Moodle to identify and remediate similar weaknesses proactively. 8. Educate users about the risks of sharing personal information and encourage strong authentication practices to reduce the risk of account compromise, which could be leveraged to exploit this vulnerability.