CVE-2012-5472 in Moodle
Summary
by MITRE
lib/formslib.php in Moodle 2.2.x before 2.2.6 and 2.3.x before 2.3.3 allows remote authenticated users to bypass intended access restrictions via a modified value of a frozen form field.
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Analysis
by VulDB Data Team • 02/24/2019
The vulnerability described in CVE-2012-5472 affects Moodle learning management systems version 2.2.x before 2.2.6 and 2.3.x before 2.3.3, specifically within the lib/formslib.php component. This represents a critical access control flaw that undermines the security model of the platform by allowing authenticated users to manipulate form field states. The issue stems from improper validation of form field properties, particularly how the system handles frozen form fields that should remain immutable during user interactions.
The technical flaw resides in the form processing logic where Moodle fails to properly validate that form fields marked as frozen cannot be modified by users during submission. When a form field is designated as frozen, it should remain in its original state regardless of client-side modifications or direct parameter manipulation. However, the vulnerable code does not adequately verify the integrity of frozen field values, allowing malicious users to submit altered values that bypass intended access restrictions. This vulnerability operates at the application layer and specifically targets the form handling mechanisms that are fundamental to user interactions within the Moodle platform.
The operational impact of this vulnerability is significant as it enables authenticated users to circumvent access controls that are typically enforced by the system. Attackers can exploit this weakness to gain unauthorized access to restricted resources or perform actions that should be limited to specific user roles. The vulnerability is particularly dangerous because it requires only authentication to exploit, meaning that any user with valid credentials can potentially bypass security controls. This could lead to unauthorized data access, modification of course content, or privilege escalation depending on the specific context of the affected forms within Moodle.
This vulnerability aligns with CWE-284 Access Control Flaws, specifically addressing improper access control mechanisms within web applications. The flaw demonstrates poor input validation and inadequate state management in form processing components, which are common patterns in web application security vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to T1078 Valid Accounts and T1566 Phishing techniques, as it allows authenticated users to leverage their legitimate credentials to bypass additional security controls. The issue also relates to T1068 Exploitation for Privilege Escalation when the bypassed restrictions involve role-based access controls or administrative functions.
The recommended mitigation strategy involves upgrading to Moodle versions 2.2.6 or 2.3.3, which contain patches addressing this specific vulnerability. Organizations should also implement additional monitoring of form submissions and access patterns to detect potential exploitation attempts. Security administrators should review and validate all form field configurations, particularly those related to access control and privilege management. Regular security assessments of web application components and input validation mechanisms should be conducted to identify similar vulnerabilities. Additionally, implementing proper session management and access control logging can help detect and respond to exploitation attempts. The vulnerability underscores the importance of proper form state management and input validation in preventing unauthorized modifications to application behavior.