CVE-2015-5272 in Moodle
Summary
by MITRE
The Forum module in Moodle 2.7.x before 2.7.10 allows remote authenticated users to post to arbitrary groups by leveraging the teacher role, as demonstrated by a post directed to "all participants."
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability identified as CVE-2015-5272 resides within the Forum module of Moodle version 2.7.x prior to 2.7.10, representing a significant access control flaw that undermines the platform's group-based security model. This issue specifically affects authenticated users who possess the teacher role, enabling them to bypass intended group restrictions and post messages to any group within a course, including groups they should not have access to. The vulnerability operates by exploiting a flaw in the forum's permission validation mechanisms, where the system fails to properly verify group membership boundaries when processing forum post requests. This allows malicious actors with teacher privileges to manipulate the target group parameter in forum posting operations, effectively circumventing the intended group isolation that Moodle's collaborative learning environment relies upon.
The technical nature of this vulnerability stems from improper input validation and privilege escalation within the forum module's backend processing logic. When a teacher attempts to post to a forum, the system should validate that the user has appropriate permissions for the target group, but this validation fails to properly enforce group boundaries. The flaw manifests when the forum module accepts and processes group identifiers without adequate authorization checks, allowing a teacher to submit a post request targeting a group that they do not belong to or have no permission to access. This represents a direct violation of the principle of least privilege and demonstrates a critical weakness in Moodle's access control implementation. The vulnerability is particularly concerning because it affects the core collaborative features of the learning management system, potentially exposing sensitive course materials and discussions to unauthorized participants.
The operational impact of CVE-2015-5272 extends beyond simple information disclosure, as it can compromise the integrity and confidentiality of educational content within Moodle environments. Teachers who exploit this vulnerability can potentially post malicious content, sensitive information, or inappropriate material to groups where such content should not be visible, undermining the trust and security that educational institutions rely upon. This flaw particularly affects courses that utilize group mode settings to separate students into different learning cohorts, such as discussion groups, project teams, or specialized classes. The vulnerability also creates potential for social engineering attacks where teachers might post misleading information to specific groups, or for information leakage where sensitive course data could be shared with unauthorized participants. Additionally, the ability to post to "all participants" groups creates a vector for mass communication that bypasses intended access controls, potentially disrupting the learning environment and violating privacy expectations.
Organizations utilizing Moodle 2.7.x versions should immediately implement mitigation strategies to address this vulnerability. The most effective immediate solution involves upgrading to Moodle 2.7.10 or later, which contains the necessary patches to fix the group permission validation flaw. System administrators should also conduct comprehensive audits of existing forum configurations to identify any instances where teachers might be able to access unintended groups. Additional mitigations include implementing stricter role management policies, monitoring forum activity logs for unusual posting patterns, and ensuring that group membership is properly reviewed and maintained. From a cybersecurity perspective, this vulnerability aligns with CWE-284, which describes improper access control, and maps to ATT&CK technique T1078 for valid accounts and privilege escalation. Organizations should also consider implementing network segmentation and access controls to limit the scope of potential exploitation, particularly in environments where multiple teachers have administrative privileges. Regular security assessments and vulnerability scanning should be conducted to identify similar flaws in other Moodle modules or components that might present similar access control vulnerabilities.