CVE-2024-0648: Yunyou CMS RCE Vulnerability

CVE-2024-0648 Overview

A critical unrestricted file upload vulnerability has been discovered in Yunyou CMS versions up to 2.2.6. This vulnerability exists in the file /app/index/controller/Common.php and allows attackers to upload arbitrary files through manipulation of the templateFile argument. The flaw can be exploited remotely without authentication, potentially leading to complete system compromise through the upload and execution of malicious code.

Critical Impact

This unrestricted file upload vulnerability enables remote attackers to upload and potentially execute malicious files on vulnerable Yunyou CMS installations, leading to full system compromise including data theft, defacement, and lateral movement within the network.

Affected Products

• Yunyou CMS versions up to and including 2.2.6
• All installations using the vulnerable /app/index/controller/Common.php component

Discovery Timeline

• 2024-01-17 - CVE-2024-0648 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0648

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The flaw resides in the Common.php controller within the Yunyou CMS application framework. The vulnerable code fails to properly validate or restrict file types during the upload process, allowing attackers to bypass security controls intended to limit uploads to safe file types.

The vulnerability is particularly severe because it requires no authentication to exploit. An attacker can remotely initiate the attack through the network-accessible upload functionality. The exploitation path through the templateFile parameter suggests the vulnerability may be related to template processing functionality, which often has elevated privileges for file operations.

Root Cause

The root cause of this vulnerability is insufficient input validation and lack of proper file type restrictions in the upload handling code within /app/index/controller/Common.php. The templateFile argument does not undergo adequate sanitization, allowing attackers to specify arbitrary file paths or upload files with dangerous extensions such as .php, .phtml, or other executable types.

This represents a failure to implement proper file upload security controls including:

• File extension whitelisting
• MIME type validation
• Content-based file type verification
• Secure storage location enforcement

Attack Vector

The attack can be initiated remotely over the network. An attacker sends a specially crafted HTTP request to the vulnerable endpoint, manipulating the templateFile parameter to upload a malicious file. Once uploaded, the attacker can access the file directly through the web server to trigger code execution.

The exploitation flow typically involves:

1. Identifying a vulnerable Yunyou CMS installation (versions ≤ 2.2.6)
2. Crafting a malicious request targeting the Common.php controller
3. Uploading a web shell or other malicious payload via the templateFile parameter
4. Accessing the uploaded file to execute arbitrary commands on the server

Technical details regarding the specific exploitation technique have been disclosed publicly. For more information, refer to the Zhaoj Blog Post or the VulDB entry #251374.

Detection Methods for CVE-2024-0648

Indicators of Compromise

• Unexpected file uploads in the CMS template directories or web-accessible locations
• Presence of PHP web shells or suspicious executable files in upload directories
• Unusual HTTP POST requests to /app/index/controller/Common.php with templateFile parameter manipulation
• Web server logs showing access to newly created .php files in unexpected locations
• Suspicious outbound connections from the web server indicating command and control activity

Detection Strategies

• Implement file integrity monitoring (FIM) on web application directories to detect unauthorized file additions
• Configure web application firewall (WAF) rules to detect and block suspicious file upload attempts and parameter tampering
• Monitor HTTP request logs for anomalous POST requests containing shell-like payloads or executable file extensions
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation activities such as web shell access

Monitoring Recommendations

• Enable detailed logging for the Yunyou CMS application and web server access logs
• Set up alerts for file creation events in web-accessible directories, particularly for executable file types
• Monitor process execution patterns from web server processes (e.g., PHP-FPM, Apache) for spawned shell processes
• Regularly audit uploaded files and template directories for unauthorized content

How to Mitigate CVE-2024-0648

Immediate Actions Required

• Identify all Yunyou CMS installations in your environment and verify version numbers
• Restrict network access to vulnerable systems until patching is complete
• Implement web application firewall rules to block malicious upload attempts
• Audit existing files in upload and template directories for indicators of prior compromise
• Consider temporarily disabling the vulnerable upload functionality if business operations permit

Patch Information

No official patch information has been provided by the vendor at the time of this writing. Organizations should monitor the official Yunyou CMS project channels for security updates. Until an official patch is available, implementing the workarounds below is strongly recommended.

For vulnerability tracking details, refer to VulDB CTI ID #251374.

Workarounds

• Implement strict file type validation at the web server level using configuration directives to block execution of uploaded files
• Configure upload directories to be non-executable using server configurations such as php_flag engine off in .htaccess
• Restrict access to the vulnerable Common.php controller via IP whitelisting or authentication requirements
• Deploy a web application firewall (WAF) with rules to block file upload attacks and shell injection patterns
• Consider placing the CMS behind a reverse proxy with additional security controls

# Apache configuration to disable PHP execution in upload directories
# Add to .htaccess or server configuration for upload directories
<Directory "/path/to/yunyou-cms/uploads">
    php_flag engine off
    <FilesMatch "\.ph(p[345]?|t|tml)$">
        Require all denied
    </FilesMatch>
</Directory>