CVE-2011-4593 in Moodle
Summary
by MITRE
Moodle 1.9.x before 1.9.15, 2.0.x before 2.0.6, and 2.1.x before 2.1.3 does not properly handle user/action_redir group messages, which allows remote authenticated users to discover e-mail addresses by visiting the messaging interface.
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Analysis
by VulDB Data Team • 12/06/2021
This vulnerability exists in Moodle learning management systems across multiple versions including 1.9.x before 1.9.15, 2.0.x before 2.0.6, and 2.1.x before 2.1.3. The flaw specifically relates to improper handling of user action_redir group messages within the messaging interface. When authenticated users access the messaging system, they can exploit this weakness to enumerate email addresses of other users within the platform. This represents a significant privacy and security concern as it violates the principle of least privilege and exposes user information that should remain confidential.
The technical implementation of this vulnerability stems from insufficient input validation and output sanitization within the messaging component of Moodle. When processing group messages with action_redir parameters, the system fails to properly restrict access to user email addresses, allowing attackers to craft specific requests that bypass normal access controls. This issue aligns with CWE-200, which addresses improper exposure of sensitive information, and specifically relates to the lack of proper access control mechanisms in the messaging subsystem. The vulnerability enables attackers to perform user enumeration attacks by simply navigating to the messaging interface and observing the responses.
The operational impact of this vulnerability is substantial for organizations relying on Moodle for educational or training purposes. Attackers can systematically discover email addresses of students, faculty, and staff members, which can then be used for social engineering attacks, spam campaigns, or targeted phishing operations. This information exposure creates additional attack vectors for threat actors who may use the discovered email addresses to conduct credential stuffing attacks against other systems or to launch more sophisticated social engineering campaigns. The vulnerability essentially provides a reconnaissance tool that undermines the security posture of educational institutions using vulnerable Moodle installations.
Organizations should immediately apply the security patches released by Moodle for versions 1.9.15, 2.0.6, and 2.1.3 to address this vulnerability. The mitigation strategy should include implementing proper access controls within the messaging interface and ensuring that user enumeration attacks are prevented through robust input validation. Network segmentation and monitoring of unusual access patterns in the messaging system can help detect potential exploitation attempts. Additionally, administrators should review and harden the messaging configuration to prevent unauthorized access to user contact information. This vulnerability demonstrates the importance of maintaining up-to-date software versions and implementing proper security controls around user information disclosure, particularly in educational platforms where user data privacy is paramount. The issue also aligns with ATT&CK technique T1087.001 for account discovery through enumeration methods that expose user information through improperly secured interfaces.