CVE-2015-4607 in Frontend User Upload Extension
Summary
by MITRE
Unrestricted file upload vulnerability in the Frontend User Upload (feupload) extension 0.5.0 and earlier for TYPO3 allows remote attackers to execute arbitrary code by uploading a file with an executable extension using a frontend form, then accessing it via a direct request to the file in the fileadmin folder.
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Analysis
by VulDB Data Team • 04/08/2019
The CVE-2015-4607 vulnerability represents a critical unrestricted file upload flaw in the TYPO3 Frontend User Upload (feupload) extension version 0.5.0 and earlier. This vulnerability exists within the TYPO3 content management system's frontend user upload functionality, creating a pathway for remote attackers to compromise systems through malicious file uploads. The issue specifically affects the extension's handling of file uploads through frontend forms, where proper validation mechanisms are either absent or insufficiently implemented. Attackers can exploit this weakness by uploading executable files with extensions that are not properly filtered, thereby bypassing security controls that should prevent such uploads.
The technical exploitation of this vulnerability occurs through a multi-step process that begins with uploading a malicious file containing executable code through the frontend form interface. The vulnerability stems from inadequate input validation and sanitization within the feupload extension, allowing attackers to bypass file type checks that should prevent the upload of potentially harmful files. Once uploaded, these files are stored in the fileadmin directory where they can be directly accessed via HTTP requests. This direct accessibility creates a persistent threat vector where attackers can execute arbitrary code by simply requesting the uploaded file through the web server, effectively turning the compromised TYPO3 installation into a command execution platform.
The operational impact of CVE-2015-4607 extends beyond simple code execution, as it provides attackers with a foothold for further system compromise. This vulnerability aligns with CWE-434 which describes "Unrestricted Upload of File with Dangerous Type" and represents a significant deviation from secure coding practices that should enforce strict file type validation and sanitization. The attack vector follows typical patterns identified in the MITRE ATT&CK framework under the T1190 technique for "Exploit Public-Facing Application" and T1059 for "Command and Scripting Interpreter." Organizations using affected TYPO3 versions face potential data breaches, system compromise, and unauthorized access to sensitive information. The vulnerability's impact is amplified by the fact that it affects the frontend upload functionality, which typically requires minimal privileges to exploit, making it particularly dangerous for web applications that allow user-generated content uploads.
Mitigation strategies for CVE-2015-4607 require immediate action to address the root cause of the vulnerability. The primary recommendation involves upgrading the feupload extension to a patched version that properly validates file types and implements strict content filtering mechanisms. Organizations should also implement additional security controls such as restricting file upload directories, implementing proper file type whitelisting, and configuring web server rules to prevent execution of uploaded files. The vulnerability demonstrates the importance of input validation and the principle of least privilege in web application security. Security measures should include regular security audits of third-party extensions, implementation of web application firewalls, and comprehensive monitoring of file upload activities. Organizations must also consider implementing mandatory file content inspection and ensuring that uploaded files are stored outside of web-accessible directories to prevent direct execution. This vulnerability underscores the critical need for proper security testing and validation of all user input in web applications, particularly those handling file uploads, as outlined in industry best practices for secure software development.