CVE-2016-2539 in ATutor
Summary
by MITRE
Cross-site request forgery (CSRF) vulnerability in install_modules.php in ATutor before 2.2.2 allows remote attackers to hijack the authentication of users for requests that upload arbitrary files and execute arbitrary PHP code via vectors involving a crafted zip file.
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Analysis
by VulDB Data Team • 01/27/2025
The CVE-2016-2539 vulnerability represents a critical cross-site request forgery flaw discovered in ATutor learning management system versions prior to 2.2.2. This vulnerability exists within the install_modules.php script and fundamentally undermines the application's security model by allowing unauthorized remote attackers to exploit legitimate user sessions. The flaw specifically targets the authentication mechanisms that should protect against unauthorized actions, creating a dangerous scenario where attackers can manipulate authenticated users into executing malicious operations without their knowledge or consent. The vulnerability operates through a sophisticated attack vector that leverages crafted zip file uploads, which then execute arbitrary PHP code on the target server, effectively granting attackers complete control over the vulnerable system.
The technical implementation of this vulnerability stems from inadequate validation of cross-site request forgery tokens within the module installation process. When users navigate to the install_modules.php endpoint, the application fails to properly verify the authenticity of incoming requests, particularly those involving file uploads and subsequent execution. This weakness enables attackers to construct malicious requests that appear legitimate to the server because they contain valid session cookies and user authentication information. The vulnerability is particularly dangerous because it combines multiple attack vectors, allowing for both file upload capabilities and arbitrary code execution within the context of an authenticated user session. The use of zip files as attack vectors demonstrates sophisticated exploitation techniques that bypass traditional file type validation mechanisms and leverage the server's decompression capabilities to execute malicious code.
The operational impact of CVE-2016-2539 extends far beyond simple data theft or session hijacking, as it provides attackers with complete system compromise capabilities. Successful exploitation allows adversaries to upload and execute arbitrary PHP code, which can result in full system control, data exfiltration, privilege escalation, and persistence mechanisms. The vulnerability affects organizations using ATutor learning management systems, potentially exposing educational institutions to significant security risks including unauthorized access to student records, course materials, and administrative functions. Given that ATutor is commonly deployed in educational environments, the impact could be severe, affecting thousands of users and potentially compromising sensitive academic data. The vulnerability also represents a significant risk to the integrity of educational content and the overall security posture of institutions relying on this platform.
Organizations should implement immediate mitigations including updating to ATutor version 2.2.2 or later, which contains the necessary patches to address the CSRF token validation issues. Additionally, implementing proper CSRF token generation and validation mechanisms, enforcing strict file upload restrictions, and deploying web application firewalls can provide additional layers of protection. The vulnerability aligns with CWE-352, which specifically addresses cross-site request forgery weaknesses, and corresponds to ATT&CK technique T1059.007 for PHP code execution. Security teams should also consider implementing network monitoring to detect suspicious file upload activities and establish proper access controls to limit the impact of potential exploitation. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in related systems and ensure comprehensive protection against similar attack vectors.