CVE-2012-4400 in Moodle
Summary
by MITRE
repository/repository_ajax.php in Moodle 2.2.x before 2.2.5 and 2.3.x before 2.3.2 allows remote authenticated users to bypass intended upload-size restrictions via a -1 value in the maxbytes field.
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Analysis
by VulDB Data Team • 12/14/2021
The vulnerability identified as CVE-2012-4400 affects Moodle learning management systems version 2.2.x prior to 2.2.5 and 2.3.x prior to 2.3.2, specifically within the repository/repository_ajax.php component. This flaw represents a critical access control weakness that allows authenticated users to circumvent configured file upload size limitations through manipulation of the maxbytes parameter. The issue stems from inadequate input validation and sanitization within the file upload processing logic, where the system fails to properly validate user-supplied values before applying them to security controls.
The technical implementation of this vulnerability exploits a design flaw in the parameter handling mechanism where the maxbytes field accepts arbitrary values without proper validation. When a user submits a value of -1 in the maxbytes field, the system interprets this as an unrestricted upload size, effectively bypassing the intended administrative limits. This behavior occurs because the application does not properly validate that the maxbytes value falls within acceptable ranges or that it conforms to expected parameter formats. The vulnerability is particularly concerning as it operates within the repository module, which is a core component of Moodle's file management and storage capabilities, making it accessible to authenticated users who may not possess elevated privileges.
The operational impact of this vulnerability extends beyond simple bypass of upload restrictions, as it creates potential for system resource exhaustion and denial of service conditions. An attacker could leverage this flaw to upload exceptionally large files, potentially consuming excessive server storage space and bandwidth resources. Additionally, the vulnerability could facilitate other attack vectors such as storage-based attacks or serve as a stepping stone for more sophisticated exploitation attempts. The security implications are exacerbated by the fact that this affects widely deployed versions of Moodle, making it a significant concern for educational institutions and organizations relying on the platform for their learning management needs.
Mitigation strategies for CVE-2012-4400 should prioritize immediate patch application to the affected Moodle versions, with administrators upgrading to the patched releases 2.2.5 and 2.3.2 respectively. Beyond patching, organizations should implement additional input validation controls within their Moodle configurations, ensuring that all user-supplied parameters undergo strict validation before being processed. Security monitoring should be enhanced to detect unusual upload patterns or parameter manipulation attempts. The vulnerability aligns with CWE-20, which addresses improper input validation, and maps to ATT&CK technique T1078 for valid accounts and T1499 for endpoint resource exhaustion. Organizations should also consider implementing network-level controls and access restrictions to limit exposure, while maintaining regular security assessments of their Moodle installations to identify similar validation weaknesses that could be exploited in other components of the system.