CVE-2012-6106 in Moodle
Summary
by MITRE
calendar/managesubscriptions.php in the Manage Subscriptions implementation in Moodle 2.4.x before 2.4.1 omits a capability check, which allows remote authenticated users to remove course-level calendar subscriptions by leveraging the student role and sending an iCalendar object.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/25/2019
The vulnerability identified as CVE-2012-6106 resides within the calendar subsystem of Moodle learning management system, specifically in the managesubscriptions.php file within the calendar module. This flaw represents a critical access control weakness that undermines the security model of the platform by allowing unauthorized users to manipulate calendar subscriptions at the course level. The vulnerability affects Moodle versions 2.4.x prior to 2.4.1, making it a significant concern for institutions running these older versions of the software.
The technical implementation flaw stems from the absence of proper capability validation within the managesubscriptions.php script. When authenticated users with the student role attempt to interact with calendar subscriptions, the system fails to verify whether the user possesses the necessary permissions to perform subscription removal operations. This missing capability check creates a direct path for privilege escalation where users can exploit the iCalendar import functionality to manipulate course-level calendar subscriptions. The vulnerability specifically manifests when users send crafted iCalendar objects that trigger the removal of existing subscriptions without proper authorization.
From an operational perspective, this vulnerability enables authenticated attackers to compromise the calendar functionality of courses they are enrolled in, potentially disrupting educational scheduling and communication. Students could remove legitimate calendar subscriptions, affecting their ability to receive important course announcements, deadlines, and events. The impact extends beyond simple disruption as it undermines the integrity of the course calendar system, potentially leading to missed assignments, lost communication channels, and compromised learning management. This weakness particularly affects institutions that rely heavily on calendar-based notifications and scheduling systems.
The vulnerability aligns with CWE-668, which describes "Exposure of Resource to Wrong Sphere," as the calendar subscription management functionality is exposed to users who should not have the ability to modify course-level subscriptions. Additionally, this issue maps to ATT&CK technique T1078.004, "Valid Accounts: Cloud Accounts," as it leverages legitimate user credentials to perform unauthorized actions within the system. Organizations should implement immediate mitigations including upgrading to Moodle 2.4.1 or later versions, applying the relevant security patches, and implementing additional monitoring for calendar subscription modifications. Network segmentation and role-based access controls should be reviewed to limit the scope of potential exploitation, while administrators should conduct regular security assessments to identify similar capability check omissions throughout the Moodle platform.
This vulnerability demonstrates the importance of comprehensive capability validation in web applications and highlights how seemingly minor security oversights can create significant operational risks in educational environments. The flaw represents a classic example of insufficient authorization checks that could be exploited to undermine the trust model of the learning management system.