CVE-2017-7321 in Revolution
Summary
by MITRE
setup/controllers/welcome.php in MODX Revolution 2.5.4-pl and earlier allows remote attackers to execute arbitrary PHP code via the config_key parameter to the setup/index.php?action=welcome URI.
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Analysis
by VulDB Data Team • 08/24/2020
The vulnerability identified as CVE-2017-7321 resides within the MODX Revolution content management system, specifically in the setup/controllers/welcome.php component of versions 2.5.4-pl and earlier. This flaw represents a critical security weakness that enables remote attackers to achieve arbitrary code execution through a carefully crafted input parameter. The vulnerability manifests when the setup/index.php script processes the config_key parameter within the context of the welcome action, creating an avenue for malicious actors to inject and execute PHP code on the target system. The issue stems from insufficient input validation and sanitization mechanisms that fail to properly filter user-supplied data before incorporating it into the application's execution flow.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common web application attack vectors. Attackers can manipulate the config_key parameter to include malicious PHP code that gets executed during the setup process. This represents a classic case of command injection or code injection vulnerability, which falls under the broader category of CWE-94 - Improper Control of Generation of Code. The vulnerability operates at the application layer and requires no authentication to exploit, making it particularly dangerous as it can be leveraged by anyone with access to the affected web application. The attack chain typically involves sending a specially crafted HTTP request containing malicious payload within the config_key parameter, which then gets processed by the vulnerable setup script and executed with the privileges of the web server.
The operational impact of CVE-2017-7321 extends far beyond simple code execution, potentially allowing full system compromise and unauthorized access to sensitive data. When successfully exploited, attackers can gain complete control over the affected server, enabling them to install backdoors, exfiltrate databases, modify content, and establish persistent access. The vulnerability's presence in the setup component means that even systems that are not currently in active setup mode could be vulnerable during the installation process or if the setup functionality remains accessible. This creates a window of opportunity for attackers to compromise systems during their initial deployment phases, which often represent the most critical period for security vulnerabilities. The impact aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: PowerShell, as the exploitation involves injecting and executing code within the application environment.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security improvements. The primary and most effective mitigation involves upgrading to MODX Revolution version 2.5.5 or later, where the vulnerability has been patched through proper input validation and sanitization measures. Organizations should also implement network-level protections such as web application firewalls that can detect and block malicious requests containing suspicious payload patterns. Additionally, security configurations should ensure that setup directories and scripts are not accessible from external networks once the initial installation is complete. The vulnerability demonstrates the importance of following secure coding practices including input validation, output encoding, and principle of least privilege. Security teams should also conduct regular vulnerability assessments and penetration testing to identify similar weaknesses in other components of their web applications, particularly focusing on parameter handling and code execution mechanisms.