CVE-2014-7831 in Moodle
Summary
by MITRE
lib/classes/grades_external.php in Moodle 2.7.x before 2.7.3 does not consider the moodle/grade:viewhidden capability before displaying hidden grades, which allows remote authenticated users to obtain sensitive information by leveraging the student role to access the get_grades web service.
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Analysis
by VulDB Data Team • 04/04/2022
The vulnerability identified as CVE-2014-7831 resides within the Moodle learning management system's grade reporting functionality, specifically in the grades_external.php file. This issue affects Moodle versions 2.7.x prior to 2.7.3 and represents a significant information disclosure flaw that undermines the system's access control mechanisms. The vulnerability stems from insufficient capability checks within the get_grades web service implementation, creating a pathway for unauthorized information retrieval that directly violates fundamental security principles of least privilege and access control.
The technical flaw manifests when authenticated users with the student role attempt to access the get_grades web service endpoint. The system fails to properly verify whether the requesting user possesses the required moodle/grade:viewhidden capability before returning grade information. This capability check is crucial because it determines whether users can view grades that have been explicitly hidden by instructors for various reasons including academic integrity, grading policy compliance, or administrative discretion. The absence of this validation means that malicious students can bypass normal access controls and obtain sensitive grade data that should remain confidential.
From an operational perspective, this vulnerability creates substantial risk for educational institutions relying on Moodle for their learning management needs. Remote authenticated users can exploit this flaw to gain unauthorized access to hidden grades, potentially compromising academic integrity and student privacy. The impact extends beyond simple information disclosure as it undermines the trust model within the learning management system, where instructors expect certain grades to remain hidden from students until appropriate times. This could affect grading policies, academic fairness, and institutional compliance with privacy regulations.
The vulnerability aligns with CWE-284, which describes improper access control issues in software systems, and represents a clear violation of the principle of least privilege. From an ATT&CK framework perspective, this vulnerability maps to T1078 legitimate credentials and T1566 valid accounts as it allows attackers to leverage existing student accounts to access information beyond their normal permissions. The security implications suggest that organizations should implement immediate mitigations including applying the available patches, reviewing access control configurations, and monitoring for unauthorized access attempts to grade information. Additionally, administrators should consider implementing network-level controls and regular security audits to detect potential exploitation attempts and maintain overall system integrity.