CVE-2016-2155 in Moodle
Summary
by MITRE
The grade-reporting feature in Singleview (aka Single View) in Moodle 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3 does not consider the moodle/grade:manage capability, which allows remote authenticated users to modify "Exclude grade" settings by leveraging the Non-Editing Instructor role.
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Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2016-2155 affects the grade-reporting functionality within Moodle's Singleview feature across multiple versions including 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3. This represents a significant authorization bypass flaw that undermines the integrity of grade management within educational platforms. The issue stems from the absence of proper capability checks within the grade reporting system, specifically the moodle/grade:manage permission that should govern access to grade modification functions. This vulnerability enables malicious actors with specific user roles to manipulate grade settings without proper authorization, creating potential security risks in academic environments where grade integrity is paramount.
The technical flaw manifests in the Singleview grade reporting feature which fails to validate whether users possess the appropriate permissions before allowing modifications to "Exclude grade" settings. This oversight allows users with the Non-Editing Instructor role to exploit the system by leveraging their existing privileges to make unauthorized grade changes. The vulnerability specifically targets the capability-based access control mechanism that should prevent unauthorized modifications to grade data, demonstrating a failure in the principle of least privilege implementation. This misconfiguration creates an attack surface where authenticated users can manipulate academic records without proper authorization, potentially leading to grade inflation or deflation scenarios.
The operational impact of this vulnerability extends beyond simple grade manipulation, affecting the overall trustworthiness of academic records within Moodle systems. Remote authenticated users can exploit this weakness to alter grade configurations that may impact student academic standing, financial aid eligibility, or graduation requirements. The Non-Editing Instructor role typically has limited permissions but the vulnerability allows these users to escalate their privileges within the grade management context. This creates a scenario where unauthorized modifications can occur without detection, potentially affecting multiple students simultaneously. The vulnerability also undermines the audit trail functionality of Moodle systems, as unauthorized changes may not be properly logged or traceable.
Organizations utilizing Moodle platforms should implement immediate mitigations including upgrading to the patched versions mentioned in the CVE description. The recommended remediation involves applying the security patches released by Moodle for versions 2.8.11, 2.9.5, and 3.0.3 to address the capability validation issue. Additionally, administrators should review user role assignments to ensure that the Non-Editing Instructor role does not inadvertently grant excessive permissions within the grade management system. The vulnerability aligns with CWE-284 which describes improper access control and represents a clear violation of the principle of least privilege. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be categorized under T1068 which involves exploiting legitimate credentials to gain higher privileges within a system. Organizations should also consider implementing additional monitoring controls to detect unauthorized grade modifications and establish proper access control policies that align with educational institution security requirements.