CVE-2016-9186 in Moodle
Summary
by MITRE
Unrestricted file upload vulnerability in the "legacy course files" and "file manager" modules in Moodle 3.1.2 allows remote authenticated users to execute arbitrary code by uploading a file with an executable extension, and then accessing it via unspecified vectors.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2016-9186 represents a critical unrestricted file upload flaw within Moodle's legacy course files and file manager modules. This security weakness exists in Moodle version 3.1.2 and affects authenticated users who can upload files to the system. The vulnerability stems from insufficient validation of file types and extensions during the upload process, allowing malicious actors to bypass security controls and introduce potentially harmful files into the platform. The flaw specifically targets the file management functionality that permits users to store and retrieve educational materials within course environments. Attackers can exploit this vulnerability by uploading malicious files with executable extensions such as .php, .asp, or .jsp, which can then be executed on the web server hosting the Moodle instance.
The technical implementation of this vulnerability involves the absence of proper file type validation mechanisms within the file upload handlers. When users upload files through the legacy course files or file manager modules, the system fails to adequately verify the actual content of uploaded files against their declared extensions. This weakness creates an environment where attackers can upload shell scripts or other malicious code disguised as legitimate files. The vulnerability's impact extends beyond simple code execution as it allows attackers to potentially gain full control over the web server hosting the Moodle application. The unspecified vectors mentioned in the description suggest that once the malicious file is uploaded and the system processes it, the attacker can access and execute the code through various pathways within the web application infrastructure. This type of vulnerability aligns with CWE-434 which specifically addresses "Unrestricted Upload of File with Dangerous Type" and represents a classic example of insecure file handling practices.
The operational impact of CVE-2016-9186 is severe and multifaceted, affecting both the integrity and availability of Moodle installations. Successful exploitation can result in complete compromise of the web server, enabling attackers to execute arbitrary commands, access sensitive user data, modify course content, and potentially establish persistent backdoors within the educational environment. The vulnerability particularly threatens educational institutions that rely heavily on Moodle for their learning management system, as it could lead to widespread data breaches affecting thousands of students and faculty members. Additionally, attackers could use the compromised system to launch further attacks against internal networks or use the platform as a staging ground for more sophisticated cyber operations. The remote authenticated nature of this vulnerability means that attackers do not require physical access to the system, making it particularly dangerous as it can be exploited from anywhere with valid user credentials. From an attack framework perspective, this vulnerability maps directly to the execution phase of the kill chain and aligns with techniques described in the MITRE ATT&CK framework under the "Execution" and "Persistence" domains, specifically targeting the "Command and Scripting Interpreter" and "Taint Shared Libraries" techniques.
Organizations affected by CVE-2016-9186 should implement immediate mitigations including the application of security patches released by Moodle developers, which typically involve enhanced file type validation and content checking mechanisms. Network administrators should also implement additional security controls such as restricting file upload capabilities to specific trusted users, implementing strict file extension whitelisting, and deploying web application firewalls to monitor and filter suspicious upload activities. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities within the platform's codebase. The implementation of principle of least privilege should be enforced, ensuring that only authorized personnel have access to file upload functionalities within the system. Additionally, organizations should establish comprehensive monitoring protocols to detect anomalous file upload activities and implement automated scanning systems to identify potentially malicious files before they can be executed. The vulnerability underscores the critical importance of maintaining up-to-date security practices and proper input validation in web applications, particularly those handling user-generated content in educational environments where data protection and privacy are paramount concerns.