CVE-2025-3647 is a medium-severity authorization 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 by educational institutions and organizations globally, including many in Europe. The vulnerability arises from insufficient authorization checks when users attempt to access cohort data. Cohorts in Moodle represent groups of users, often used to manage permissions and access to courses or resources collectively. Due to this flaw, users with certain privileges can retrieve cohort information they are not authorized to access, potentially exposing sensitive user group data. The CVSS 3.1 base score of 4.3 reflects a medium severity, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and limited confidentiality impact (C:L), with no integrity or availability impact (I:N/A:N). Exploitation does not require user interaction but does require some level of authenticated access with limited privileges. There are no known exploits in the wild at the time of publication, and no patches or vendor advisories were linked in the provided data. The vulnerability primarily affects confidentiality by allowing unauthorized disclosure of cohort membership data, which could be leveraged for further reconnaissance or social engineering attacks within educational environments.

For European organizations, especially educational institutions and training providers that rely heavily on Moodle, this vulnerability could lead to unauthorized disclosure of cohort membership information. This data might include student or staff groupings, enrollment details, or access groupings that could be sensitive. Exposure of such information could facilitate targeted phishing attacks, privacy violations under GDPR, and undermine trust in the institution's data protection practices. While the vulnerability does not allow modification or disruption of services, the confidentiality breach could have reputational and compliance consequences. Institutions with large user bases or those handling sensitive educational or personal data are at higher risk. Additionally, since Moodle is widely adopted in countries with strong data protection regulations, any data leakage could trigger regulatory scrutiny and potential fines. The impact is primarily on confidentiality with no direct effect on system integrity or availability.

To mitigate this vulnerability, European organizations should: 1) Immediately verify the Moodle version in use and plan for an upgrade to a patched version once available. Since no patch links were provided, organizations should monitor official Moodle security advisories and repositories for updates addressing CVE-2025-3647. 2) In the interim, restrict access to cohort data by reviewing and tightening role-based permissions, ensuring that only trusted users have privileges that allow cohort data access. 3) Implement additional access control layers or custom plugins that enforce stricter authorization checks on cohort data retrieval if feasible. 4) Conduct audits of user access logs to detect any unusual access patterns to cohort data that could indicate exploitation attempts. 5) Educate administrative users about the risk and encourage vigilance against social engineering that might leverage exposed cohort information. 6) Ensure that data protection officers are informed to assess compliance risks and prepare for potential incident response. 7) Consider network-level controls to limit access to Moodle administrative interfaces to trusted IP ranges where possible.