CVE-2013-2083 in Moodle
Summary
by MITRE
The MoodleQuickForm class in lib/formslib.php in Moodle through 2.1.10, 2.2.x before 2.2.10, 2.3.x before 2.3.7, and 2.4.x before 2.4.4 does not properly handle a certain array-element syntax, which allows remote attackers to bypass intended form-data filtering via a crafted request.
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Analysis
by VulDB Data Team • 01/02/2022
The vulnerability identified as CVE-2013-2083 affects Moodle learning management systems across multiple version ranges, specifically impacting versions through 2.1.10, 2.2.x before 2.2.10, 2.3.x before 2.3.7, and 2.4.x before 2.4.4. This issue resides within the MoodleQuickForm class implementation in the lib/formslib.php file, representing a critical security flaw that undermines the platform's form validation and data filtering mechanisms. The vulnerability stems from improper handling of array-element syntax during form processing, creating a pathway for malicious actors to circumvent security controls that are meant to sanitize and validate user input before it is processed by the system.
The technical flaw manifests when the MoodleQuickForm class encounters specific array-element syntax patterns in HTTP requests that are not properly normalized or validated before being processed. This misconfiguration allows attackers to craft malicious requests containing specially formatted array elements that bypass the intended filtering mechanisms designed to prevent unauthorized data manipulation. The vulnerability operates at the input validation layer, where the system should have rejected or sanitized malformed array syntax but instead accepted it as legitimate input. This behavior creates a condition where attacker-controlled data can flow through the application's form processing pipeline without proper sanitization, potentially leading to various downstream security consequences including data injection, privilege escalation, or information disclosure.
The operational impact of this vulnerability extends beyond simple data validation bypass, as it represents a fundamental flaw in the application's security architecture that affects core form handling functionality. Remote attackers can exploit this weakness to submit crafted requests that manipulate form data in ways that were not intended by the application's developers, potentially allowing them to inject malicious content or manipulate application behavior. The vulnerability's persistence across multiple version lines indicates it was a systemic issue in the form processing logic rather than a one-time coding error, making it particularly concerning for organizations running affected Moodle installations. This flaw directly violates security principles established in CWE-20, which addresses "Improper Input Validation" and represents a classic example of how insufficient sanitization can compromise application integrity and user data protection.
Organizations affected by CVE-2013-2083 should implement immediate mitigations including upgrading to patched versions of Moodle where available, as the vulnerability was addressed through proper input sanitization and array handling in subsequent releases. Security teams should also consider implementing network-level protections such as web application firewalls that can detect and block suspicious array-element patterns in HTTP requests. Additionally, administrators should review and audit existing form processing logic to ensure that similar vulnerabilities do not exist in custom plugins or modifications. The vulnerability's classification under ATT&CK technique T1059.008, which covers "Command and Scripting Interpreter: PowerShell," suggests that attackers might leverage such form manipulation capabilities to execute unauthorized operations within the application context, making immediate remediation critical for maintaining system integrity and protecting against potential exploitation.