CVE-2011-4301 in Moodle
Summary
by MITRE
The MoodleQuickForm class in the Forms Library in lib/formslib.php in Moodle 1.9.x before 1.9.14, 2.0.x before 2.0.5, and 2.1.x before 2.1.2 does not recognize Forms API setConstant operations, which allows remote attackers to submit unexpected form content by modifying the values of constant fields.
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Analysis
by VulDB Data Team • 12/05/2021
The vulnerability described in CVE-2011-4301 represents a critical flaw in Moodle's form handling mechanism that affects multiple versions of the popular learning management system. This issue stems from the MoodleQuickForm class implementation within the Forms Library located in lib/formslib.php, where the system fails to properly validate or recognize constant form fields during the form processing lifecycle. The vulnerability specifically targets the Forms API's setConstant operations, which are designed to establish fields that should remain immutable during form submission. When these operations are not properly recognized, attackers can manipulate form data by altering the values of fields that should remain constant, thereby bypassing intended security controls.
The technical exploitation of this vulnerability occurs through manipulation of form field values during HTTP requests, allowing remote attackers to inject unexpected content into forms that should maintain their original constant values. This flaw essentially creates a bypass mechanism where attackers can modify form parameters that the system should have ignored or validated as immutable. The impact extends across Moodle versions 1.9.x prior to 1.9.14, 2.0.x prior to 2.0.5, and 2.1.x prior to 2.1.2, indicating a widespread issue affecting the core form processing functionality that is fundamental to Moodle's operation. This vulnerability directly relates to CWE-20, which describes improper input validation, and represents a classic case of insufficient validation of form field data integrity.
The operational impact of this vulnerability is significant for organizations using affected Moodle versions, as it allows attackers to potentially manipulate form submissions that control user permissions, grade assignments, or modify system configurations. Attackers could exploit this to submit unauthorized data that bypasses normal form validation checks, potentially leading to privilege escalation or data corruption. The vulnerability is particularly concerning because it operates at the form processing layer, meaning it can affect multiple components of the Moodle system that rely on proper form validation. This issue aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage and T1566 for credential access through form manipulation, as it enables attackers to craft malicious form submissions that could be processed without proper validation.
Organizations affected by this vulnerability should immediately implement mitigation strategies including updating to patched versions of Moodle, applying the official security patches released by the Moodle development team, and implementing additional input validation measures at the application level. System administrators should also conduct thorough security assessments of their Moodle installations to identify any potential exploitation attempts and monitor form submission logs for suspicious activity. The vulnerability highlights the importance of proper form field validation and the need for robust input sanitization in web applications, particularly those handling user data and administrative functions. Regular security updates and patch management processes should be reinforced to prevent similar vulnerabilities from being exploited in the future, as this issue demonstrates how fundamental framework components can introduce security risks when validation controls are insufficiently implemented.