CVE-2014-3553 in Moodle
Summary
by MITRE
mod/forum/classes/post_form.php in Moodle through 2.3.11, 2.4.x before 2.4.11, 2.5.x before 2.5.7, 2.6.x before 2.6.4, and 2.7.x before 2.7.1 does not enforce the moodle/site:accessallgroups capability requirement before proceeding with a post to all groups, which allows remote authenticated users to bypass intended access restrictions by leveraging two or more group memberships.
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Analysis
by VulDB Data Team • 06/04/2017
The vulnerability described in CVE-2014-3553 affects the Moodle learning management system and represents a significant access control flaw that undermines the platform's group-based security model. This issue exists within the mod/forum/classes/post_form.php component, which handles forum posting functionality across multiple Moodle versions including 2.3.11 and earlier, 2.4.x versions before 2.4.11, 2.5.x versions before 2.5.7, 2.6.x versions before 2.6.4, and 2.7.x versions before 2.7.1. The flaw specifically relates to how the system validates user permissions when attempting to post messages to all groups within a course context.
The technical implementation of this vulnerability stems from the absence of proper capability checks within the forum posting form processing logic. When users attempt to post to all groups, the system should verify that they possess the moodle/site:accessallgroups capability, which is a fundamental permission required to bypass individual group restrictions. However, the code fails to enforce this validation, allowing authenticated users to circumvent intended access controls even when they lack the appropriate permissions. This occurs because users with membership in two or more groups can exploit the missing validation to post messages across all groups without proper authorization.
From an operational perspective, this vulnerability creates a serious risk for educational institutions using Moodle as their primary learning platform. An attacker with legitimate user credentials but without elevated privileges can potentially disseminate information across multiple course groups, effectively bypassing the group isolation that Moodle is designed to maintain. This could lead to unauthorized disclosure of sensitive course materials, discussion content, or announcements intended for specific student populations. The impact extends beyond simple information disclosure as it undermines the fundamental security model that separates student populations and maintains privacy within different learning contexts.
The vulnerability aligns with CWE-284, which describes improper access control issues where systems fail to properly enforce authorization checks. From an attack framework perspective, this flaw maps to techniques described in the MITRE ATT&CK framework under privilege escalation and defense evasion categories, as it allows authenticated users to gain access to resources they should not be authorized to access. The attack vector is particularly concerning because it requires only legitimate user authentication, making it difficult to detect through traditional security monitoring approaches. Organizations should implement immediate mitigations including updating to patched versions of Moodle, reviewing and strengthening group membership permissions, and conducting security audits of forum configurations to ensure proper capability enforcement is in place.
The remediation strategy should prioritize applying the official patches released by Moodle for the affected versions, as these updates specifically address the missing capability validation in the post_form.php component. Additionally, administrators should conduct comprehensive reviews of their Moodle installations to ensure that all forum-related capabilities are properly configured and that users cannot bypass group access controls through similar mechanisms. Security monitoring should be enhanced to detect unusual posting patterns across multiple groups, and regular security assessments should be performed to identify potential privilege escalation vectors within the learning management system infrastructure.