CVE-2019-10134 in Moodle
Summary
by MITRE
A flaw was found in Moodle before 3.7, 3.6.4, 3.5.6, 3.4.9 and 3.1.18. The size of users' private file uploads via email were not correctly checked, so their quota allowance could be exceeded.
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Analysis
by VulDB Data Team • 09/09/2025
The vulnerability identified as CVE-2019-10134 represents a critical file system security flaw within the Moodle learning management system that affects multiple versions prior to specific patch releases. This issue stems from inadequate validation mechanisms in the email-based file upload functionality, where user-submitted private files are not properly constrained against size limitations. The flaw exists in the core file handling architecture of Moodle, specifically within the email-to-file upload pathway that allows users to submit files through email attachments to their private file areas. This vulnerability falls under the category of improper input validation as defined by CWE-20, where the system fails to adequately check or sanitize the size parameters of uploaded files. The issue is particularly concerning because it directly impacts the quota enforcement mechanisms that are fundamental to maintaining system storage integrity and preventing unauthorized resource consumption.
The technical implementation of this vulnerability occurs when users attempt to upload private files through email functionality without proper size validation checks. The system accepts file uploads regardless of their actual size, allowing malicious actors or users with malicious intent to exceed their allocated storage quotas significantly. This flaw operates at the intersection of file system management and user access control, where the quota enforcement mechanism fails to properly validate file sizes against user limitations. The vulnerability is classified as a resource exhaustion issue that can lead to denial of service conditions and unauthorized storage consumption. According to ATT&CK framework, this represents a privilege escalation vector through resource abuse, specifically under the technique of "Resource Hijacking" where attackers can consume excessive system resources beyond normal operational limits.
The operational impact of CVE-2019-10134 extends beyond simple storage consumption issues, potentially leading to system instability, performance degradation, and service disruption for legitimate users. When users exceed their allocated quotas, the system may experience cascading failures where legitimate file operations become impossible due to storage exhaustion. This vulnerability can be exploited by attackers to create denial of service conditions by uploading large files that consume storage space beyond normal limits, effectively preventing other users from accessing their own files or uploading new content. The flaw also creates potential data integrity issues when storage limits are exceeded, as the system may not properly handle file allocation failures or maintain consistent file system states. Organizations relying on Moodle for educational or training purposes face significant operational risks, as this vulnerability can compromise the entire learning management platform's availability and reliability.
Mitigation strategies for CVE-2019-10134 require immediate implementation of patch updates to the affected Moodle versions, with administrators prioritizing deployment of the latest stable releases that contain the necessary fixes. The recommended approach includes applying the official security patches provided by Moodle developers, which typically involve implementing proper file size validation checks and strengthening quota enforcement mechanisms. System administrators should also consider implementing additional monitoring controls to detect unusual file upload patterns or storage consumption that might indicate exploitation attempts. Network-level controls can be deployed to limit email-to-file upload functionality where possible, and organizations should establish automated alerting mechanisms for storage usage thresholds. The fix addresses the root cause by ensuring that file size parameters are properly validated before allocation, implementing proper input sanitization, and strengthening the quota enforcement logic to prevent unauthorized consumption of system resources. Organizations should also conduct thorough security assessments to identify any potential exploitation that may have already occurred and implement comprehensive logging of file upload activities for forensic analysis.