CVE-2015-5331 in Moodle
Summary
by MITRE
Moodle 2.9.x before 2.9.3 does not properly check the contact list before authorizing message transmission, which allows remote authenticated users to bypass intended access restrictions and conduct spam attacks via the messaging API.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability identified as CVE-2015-5331 affects Moodle version 2.9.x prior to 2.9.3 and represents a critical authorization flaw within the messaging system that undermines the platform's security controls. This issue stems from insufficient validation of contact lists during message transmission processes, creating a pathway for malicious actors to exploit the system's access controls. The flaw specifically targets the messaging API component of Moodle, which serves as the backbone for user communication within the learning management system environment. Security researchers have classified this vulnerability as a weakness in access control mechanisms that directly impacts the integrity of user communications and system security posture.
The technical implementation of this vulnerability occurs when authenticated users leverage the messaging API to send messages without proper validation of recipient permissions or contact list restrictions. This flaw allows attackers to bypass intended access controls that should prevent users from sending messages to unauthorized recipients or groups. The vulnerability operates at the application layer and requires authentication to exploit, making it particularly dangerous as it can be leveraged by legitimate users who have gained access to the system through other means. The flaw essentially permits unauthorized message routing through the system's contact validation mechanisms, creating opportunities for spam attacks and potential data exfiltration through messaging channels.
From an operational impact perspective, this vulnerability enables malicious actors to conduct spam attacks on large user bases within Moodle environments, potentially disrupting educational services and compromising user privacy. The ability to bypass contact list restrictions means that attackers can flood users with unwanted messages, creating denial of service conditions and potentially spreading malicious content through the messaging system. Organizations using affected Moodle versions face significant risks including reputational damage, user trust erosion, and potential compliance violations when user communications are compromised. The vulnerability also creates opportunities for social engineering attacks where malicious users can exploit the messaging system to target specific individuals or groups within the educational institution.
The security implications extend beyond simple spam delivery to encompass broader access control violations that align with common attack patterns documented in the attack framework. This vulnerability demonstrates weaknesses in input validation and authorization checks that are commonly addressed through proper implementation of the principle of least privilege. Organizations should implement immediate mitigation strategies including updating to Moodle version 2.9.3 or later, which contains the necessary patches to address the contact list validation issue. Additional protective measures include implementing monitoring of messaging API usage patterns, restricting API access to trusted sources, and conducting regular security audits of communication systems. The vulnerability also highlights the importance of proper access control implementation and the need for comprehensive testing of authorization mechanisms within web applications. Security professionals should reference the CWE database for related weakness classifications and consider implementing defensive measures aligned with ATT&CK framework methodologies for preventing unauthorized access to communication systems.