CVE-2017-9069 in Revolution
Summary
by MITRE
In MODX Revolution before 2.5.7, a user with file upload permissions is able to execute arbitrary code by uploading a file with the name .htaccess.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-9069 represents a critical security flaw in MODX Revolution content management systems prior to version 2.5.7. This vulnerability arises from inadequate input validation and file handling mechanisms within the system's file upload functionality. The flaw specifically targets users who possess file upload permissions, creating a privilege escalation scenario that allows malicious actors to execute arbitrary code on the affected system. The vulnerability is particularly concerning because it leverages the .htaccess file extension, which is commonly used in web server configurations and typically processed by Apache servers with specific security implications.
The technical implementation of this vulnerability stems from the system's failure to properly sanitize file names during the upload process. When a user with appropriate permissions uploads a file named .htaccess, the system does not adequately validate or restrict the file type, allowing the upload to proceed despite the potentially dangerous nature of the file extension. This oversight creates an execution path where the uploaded .htaccess file can be processed by the web server and potentially interpreted as an Apache configuration file that could contain malicious directives. The vulnerability is classified under CWE-434 as Unrestricted Upload of File with Dangerous Type, which specifically addresses the risk of uploading files that can be executed or interpreted by the web server. The flaw allows for arbitrary code execution because Apache servers treat .htaccess files specially, processing their contents as configuration directives that can include script execution commands or other malicious code.
The operational impact of this vulnerability is severe and multifaceted. An attacker with file upload privileges can effectively gain full control over the web server hosting the MODX installation by uploading a malicious .htaccess file. This file can contain various malicious directives including but not limited to command execution, file inclusion, or redirection attacks that compromise the entire server. The vulnerability can be exploited to establish persistent backdoors, exfiltrate sensitive data, or launch further attacks against internal network resources. The attack surface is particularly broad because many MODX installations allow users with basic content management permissions to upload files, making this vulnerability exploitable by individuals who should not have the ability to execute arbitrary code on the server. From an ATT&CK framework perspective, this vulnerability maps to T1059.001 Command and Scripting Interpreter and T1078 Valid Accounts, as it allows for command execution through legitimate user accounts with file upload permissions.
Mitigation strategies for CVE-2017-9069 should focus on both immediate patching and architectural improvements. The primary recommendation is to upgrade to MODX Revolution version 2.5.7 or later, which includes proper input validation and file name sanitization for .htaccess files. Organizations should also implement additional security measures such as restricting file upload capabilities to only trusted administrators, implementing strict file type validation that explicitly blocks .htaccess file uploads, and configuring web server security settings to prevent execution of configuration files in upload directories. Network segmentation and monitoring should be employed to detect unauthorized file upload activities, while regular security audits should verify that no malicious .htaccess files have been successfully uploaded. The vulnerability highlights the importance of principle of least privilege and proper input validation, as recommended by security frameworks such as OWASP Top 10 and NIST Cybersecurity Framework. Organizations should also consider implementing web application firewalls and file integrity monitoring systems to detect and prevent exploitation attempts.