CVE-2025-67853 is a vulnerability identified in the Moodle learning management system (LMS), specifically affecting versions 4.1.0, 4.4.0, 4.5.0, 5.0.0, and 5.1.0. The root cause is the improper restriction of excessive authentication attempts in the confirmation email service, which lacks adequate rate limiting controls. This deficiency allows remote attackers to perform brute-force attacks by repeatedly attempting to confirm email addresses or guess user credentials without triggering lockouts or delays. The vulnerability does not require any privileges or user interaction, making it remotely exploitable over the network. The CVSS v3.1 base score of 7.5 reflects a high severity, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), high confidentiality impact (C:H), and no impact on integrity or availability (I:N/A:N). Exploiting this flaw can lead to unauthorized disclosure of user account information, facilitating further attacks such as account takeover or phishing. Although no public exploits are currently known, the vulnerability's nature and ease of exploitation make it a significant threat to Moodle deployments. The lack of patch links suggests that fixes may be pending or need to be obtained from Moodle's official channels. Organizations relying on Moodle for education or training should prioritize addressing this issue to prevent credential compromise.

For European organizations, the impact of CVE-2025-67853 is considerable, especially for educational institutions, government agencies, and enterprises using Moodle as their LMS. Successful exploitation can lead to unauthorized access to user accounts, exposing sensitive personal data, academic records, and internal communications. This breach of confidentiality could result in reputational damage, regulatory penalties under GDPR, and potential disruption of educational services. Attackers could leverage compromised accounts to escalate privileges, conduct phishing campaigns, or move laterally within networks. The absence of integrity and availability impacts limits direct system disruption, but the confidentiality breach alone poses a serious risk. Given Moodle's widespread adoption in Europe, particularly in countries with strong e-learning infrastructures, the threat could affect a large user base. The vulnerability also increases the attack surface for cybercriminals targeting educational data and intellectual property. Organizations may face increased incident response costs and the need for enhanced security monitoring if exploitation occurs.

To mitigate CVE-2025-67853 effectively, organizations should: 1) Apply official patches or updates from Moodle as soon as they become available to address the rate limiting flaw. 2) Implement custom rate limiting or throttling mechanisms on the confirmation email service to restrict the number of authentication attempts per IP address or user account within a given timeframe. 3) Deploy web application firewalls (WAFs) with rules to detect and block brute-force patterns targeting the confirmation email endpoints. 4) Enable multi-factor authentication (MFA) for Moodle user accounts to reduce the risk of account compromise even if credentials are guessed. 5) Monitor logs and alerts for abnormal authentication attempts or spikes in confirmation email requests. 6) Educate users about phishing risks and encourage strong, unique passwords. 7) Conduct regular security assessments and penetration tests focusing on authentication mechanisms. 8) Segment Moodle infrastructure from critical internal networks to limit lateral movement in case of compromise. These measures go beyond generic advice by focusing on the specific vulnerable service and attack vectors.