CVE-2018-12491 in PHPOK
Summary
by MITRE
PHPOK 4.9.032 has an arbitrary file upload vulnerability in the import_f function in framework/admin/modulec_control.php, as demonstrated by uploading a .php file within a .php.zip archive, a similar issue to CVE-2018-8944.
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Analysis
by VulDB Data Team • 02/19/2020
The vulnerability CVE-2018-12491 represents a critical arbitrary file upload flaw in PHPOK version 4.9.032 that resides within the import_f function of the framework/admin/modulec_control.php file. This vulnerability allows attackers to execute malicious code by uploading PHP files through the application's import functionality, creating a severe security risk that can lead to complete system compromise. The issue manifests when a malicious user uploads a .php file contained within a .php.zip archive, exploiting the lack of proper file type validation and sanitization mechanisms. This vulnerability directly relates to the well-known CWE-434 which describes insecure file upload vulnerabilities where applications accept files without proper validation, allowing potentially malicious content to be executed on the server. The attack vector leverages the application's trust in file extensions and lacks proper content inspection, making it particularly dangerous for web applications that handle user-uploaded content.
The technical exploitation of this vulnerability occurs through the import_f function that processes file uploads without adequate security checks. When a user uploads a .php.zip archive, the application extracts and processes the contents without proper validation of the file types or content, allowing the PHP file to be executed on the server. This represents a classic case of insufficient input validation and improper file handling, where the application fails to verify that uploaded files conform to expected security parameters. The vulnerability's similarity to CVE-2018-8944 demonstrates a pattern of insecure file upload implementations in PHP applications, where the import functionality does not properly sanitize or validate file extensions, file contents, or archive structures. This flaw enables attackers to bypass normal security controls and gain unauthorized access to the server environment.
The operational impact of CVE-2018-12491 is severe and far-reaching, as successful exploitation can result in complete system compromise, data theft, and unauthorized access to sensitive information. Attackers can upload backdoor scripts, web shells, or other malicious payloads that persist on the server and provide ongoing access to the compromised system. The vulnerability creates a persistent threat that can be exploited repeatedly, potentially allowing attackers to establish a foothold for further attacks within the network infrastructure. Organizations using affected PHPOK versions face significant risks including unauthorized data access, system integrity compromise, and potential regulatory violations due to security breaches. The vulnerability also enables attackers to perform privilege escalation attacks and potentially gain administrative access to the application, leading to complete control over the web server environment. According to ATT&CK framework, this vulnerability maps to T1059.007 (Command and Scripting Interpreter: PowerShell) and T1505.003 (Server Software Component: Web Shell) techniques, as attackers can leverage the uploaded PHP files to execute commands and maintain persistence.
Mitigation strategies for CVE-2018-12491 must address both immediate remediation and long-term security improvements. The primary solution involves applying the vendor-provided security patch or upgrading to a patched version of PHPOK that properly validates and sanitizes file uploads. Organizations should implement comprehensive file validation mechanisms that check file extensions, MIME types, and file contents against known good patterns rather than relying on simple extension checks. Additional security measures include restricting file upload directories, implementing proper file permissions, and using secure file handling practices such as storing uploaded files outside the web root. Network-based protections such as web application firewalls can help detect and block malicious upload attempts, while regular security audits and penetration testing should be conducted to identify similar vulnerabilities. The implementation of proper input validation, as defined by CWE-170 standards, and adherence to secure coding practices are essential for preventing similar vulnerabilities from occurring in the future. Organizations should also consider implementing automated security scanning tools that can detect insecure file upload functions and provide real-time monitoring of file upload activities to prevent exploitation attempts.