CVE-2018-16974 in Elefant
Summary
by MITRE
An issue was discovered in Elefant CMS before 2.0.7. There is a PHP Code Execution Vulnerability in apps/filemanager/upload/drop.php by using /filemanager/api/rm/.htaccess to remove the .htaccess file, and then using a filename that ends in .php followed by space characters (for bypassing the blacklist).
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Analysis
by VulDB Data Team • 05/16/2023
The vulnerability CVE-2018-16974 represents a critical PHP code execution flaw in Elefant CMS versions prior to 2.0.7, demonstrating a sophisticated attack vector that combines file manipulation with bypass techniques. This vulnerability exists within the filemanager application's upload functionality, specifically in the drop.php endpoint which handles file uploads through the /filemanager/api/rm/ path. The flaw allows attackers to execute arbitrary PHP code by leveraging a multi-step exploitation technique that manipulates the application's file handling mechanisms. The vulnerability is particularly concerning because it operates at the core of content management system functionality where file uploads are routinely processed, making it a prime target for attackers seeking persistent access to web applications.
The technical implementation of this vulnerability exploits a combination of directory traversal and filename manipulation techniques to bypass security restrictions. Attackers can first remove the .htaccess file using the rm/ endpoint which typically handles file removal operations, effectively disabling security measures that would normally prevent PHP file execution. Following this removal, attackers can upload a file with a name ending in .php followed by space characters to bypass the application's blacklist filtering mechanism. The space character bypass works because the filtering logic may not properly sanitize or normalize the filename before processing, allowing malicious PHP code to be executed as a legitimate web script. This technique aligns with common web application attack patterns documented in the attack tree framework and represents a form of input validation bypass that falls under CWE-15 Input Validation and Whitelisting.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with complete control over the affected web server environment. Once successfully exploited, attackers can execute arbitrary commands on the server, potentially leading to data theft, service disruption, or further network infiltration. The vulnerability's persistence mechanism through .htaccess file manipulation means that even if the initial attack is detected and mitigated, the attacker can maintain access by ensuring the malicious file execution environment remains intact. This aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1566 for Phishing with Malicious Attachments, as the vulnerability enables both direct execution and the delivery of additional malicious payloads. The attack vector is particularly dangerous in shared hosting environments or when the CMS is deployed with elevated privileges, as it can lead to complete system compromise.
Mitigation strategies for CVE-2018-16974 must address both the immediate vulnerability and the underlying architectural issues that allowed the bypass to succeed. The primary remediation involves upgrading to Elefant CMS version 2.0.7 or later, which includes proper input sanitization and enhanced file validation mechanisms. Organizations should implement comprehensive file upload restrictions including strict filename validation, MIME type checking, and the removal of executable file extensions from upload capabilities. Additional protective measures include disabling PHP execution in upload directories, implementing proper access controls for file management operations, and deploying web application firewalls to detect and block suspicious upload patterns. The vulnerability highlights the importance of proper input validation and the principle of least privilege in web application security, as outlined in security frameworks such as OWASP Top 10 and NIST Cybersecurity Framework. Regular security audits and penetration testing should be conducted to identify similar validation bypass opportunities, particularly in applications that handle user-supplied file uploads or directory operations.