CVE-2023-50564: Pluck-CMS Pluck RCE Vulnerability

CVE-2023-50564 Overview

CVE-2023-50564 is an arbitrary file upload vulnerability affecting the /inc/modules_install.php component of Pluck-CMS v4.7.18. This vulnerability allows authenticated attackers to execute arbitrary code on the target server by uploading a specially crafted ZIP file containing malicious content. The flaw stems from insufficient validation of uploaded files during the module installation process.

Critical Impact

Attackers with low-level privileges can achieve remote code execution by exploiting the insecure file upload mechanism, potentially leading to complete server compromise.

Affected Products

• Pluck-CMS Pluck v4.7.18
• Pluck-CMS module installation component (/inc/modules_install.php)

Discovery Timeline

• 2023-12-14 - CVE-2023-50564 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-50564

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The module installation functionality in Pluck-CMS v4.7.18 fails to properly validate the contents of uploaded ZIP files before extracting them to the web-accessible directory. An attacker with authenticated access to the CMS administrative interface can exploit this weakness by crafting a malicious ZIP archive containing executable PHP files disguised as legitimate module components.

Upon extraction, these malicious files are placed in a location accessible via the web server, enabling the attacker to trigger code execution by requesting the uploaded script. The network-based attack vector requires only low privileges, making this vulnerability particularly dangerous for multi-user CMS deployments where administrative access may be shared or compromised.

Root Cause

The root cause of this vulnerability lies in the inadequate input validation within the modules_install.php component. The CMS does not properly inspect or sanitize the contents of uploaded ZIP files before extraction. Specifically, the code fails to:

1. Validate file extensions within the ZIP archive against an allowlist
2. Check for executable file types such as .php, .phtml, or other server-side scripts
3. Implement proper path traversal protections during extraction
4. Verify the integrity and structure of uploaded module packages

Attack Vector

The attack is executed over the network and requires authenticated access to the Pluck-CMS administrative panel. An attacker crafts a malicious ZIP file containing a PHP web shell or other executable payload, then uploads it through the module installation interface. The insufficient validation allows the malicious files to be extracted to the web root, where they can be accessed and executed remotely.

The exploitation process involves:

1. Authenticating to the Pluck-CMS admin panel with valid credentials
2. Navigating to the module installation functionality
3. Uploading a crafted ZIP file containing a PHP web shell
4. Accessing the extracted malicious file via direct URL request
5. Executing arbitrary commands on the underlying server

Technical details and proof-of-concept information are available in the GitHub PoC Exploit for PluckCMS and the CVE-2023-50564 PoC repository.

Detection Methods for CVE-2023-50564

Indicators of Compromise

• Unexpected PHP files appearing in the modules or web-accessible directories
• Unusual HTTP requests to newly created files within the CMS installation
• Web shell signatures or encoded PHP code in uploaded module packages
• Suspicious process execution originating from the web server user context

Detection Strategies

• Monitor file system changes in the Pluck-CMS installation directory, particularly for new .php files
• Implement web application firewall (WAF) rules to detect malicious file upload attempts
• Review web server access logs for requests to unexpected endpoints within the CMS structure
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation activity

Monitoring Recommendations

• Enable detailed logging for the module installation functionality
• Configure alerts for file creation events in the CMS modules directory
• Monitor for outbound connections from the web server that may indicate command-and-control communication
• Implement integrity monitoring for critical CMS files and directories

How to Mitigate CVE-2023-50564

Immediate Actions Required

• Restrict access to the Pluck-CMS administrative panel to trusted IP addresses only
• Implement strong authentication mechanisms and review all admin user accounts
• Consider disabling the module installation functionality if not actively required
• Deploy web application firewall rules to block malicious file upload attempts

Patch Information

Users should upgrade Pluck-CMS to the latest available version that addresses this vulnerability. Check the official Pluck-CMS repository for security updates and patched releases. Given the availability of public proof-of-concept exploits, upgrading should be treated as a high priority.

Workarounds

• Implement server-side file type validation to restrict uploads to approved file types only
• Configure the web server to prevent execution of scripts in upload directories using .htaccess or equivalent directives
• Remove or rename the modules_install.php file if module installation functionality is not required
• Apply filesystem permissions to restrict write access to sensitive directories

# Example: Disable PHP execution in modules directory (Apache)
# Add to .htaccess in the modules directory
# php_flag engine off

# Example: Restrict access to admin panel by IP
# <Directory /path/to/pluck/admin>
#     Require ip 192.168.1.0/24
# </Directory>