CVE-2024-51053: AVSCMS File Upload RCE Vulnerability

CVE-2024-51053 Overview

CVE-2024-51053 is an arbitrary file upload vulnerability affecting AVSCMS v8.2.0. The vulnerability exists in the /main/fileupload.php component, which fails to properly validate uploaded files. This flaw allows unauthenticated remote attackers to upload crafted malicious files to the server, enabling arbitrary code execution within the context of the web application.

Critical Impact

Unauthenticated attackers can exploit this vulnerability to upload malicious files and achieve remote code execution on vulnerable AVSCMS installations, potentially leading to complete server compromise.

Affected Products

• AVSCMS v8.2.0
• Potentially other versions of AVSCMS with the same vulnerable /main/fileupload.php component

Discovery Timeline

• 2024-11-18 - CVE-2024-51053 published to NVD
• 2024-11-19 - Last updated in NVD database

Technical Details for CVE-2024-51053

Vulnerability Analysis

This arbitrary file upload vulnerability stems from insufficient validation in the file upload functionality of AVSCMS v8.2.0. The /main/fileupload.php component does not properly verify the type, content, or extension of uploaded files before accepting them. This allows attackers to bypass intended security restrictions and upload executable scripts or other malicious payloads directly to the web server.

The vulnerability requires no authentication, meaning any remote attacker with network access to the vulnerable application can exploit it. Once a malicious file (such as a PHP web shell) is successfully uploaded, the attacker can execute arbitrary commands on the underlying server with the privileges of the web server process.

Root Cause

The root cause of this vulnerability is improper input validation in the file upload handler located at /main/fileupload.php. The component fails to implement adequate security controls such as:

• File type validation based on content (magic bytes)
• Allowlisting of permitted file extensions
• Proper sanitization of uploaded filenames
• Upload directory restrictions preventing script execution

This lack of validation allows attackers to upload files with executable extensions (e.g., .php) containing malicious code.

Attack Vector

The attack is network-based and can be executed by unauthenticated remote attackers. The exploitation process typically follows this pattern:

1. The attacker identifies a vulnerable AVSCMS v8.2.0 installation with the exposed /main/fileupload.php endpoint
2. A crafted HTTP request is sent containing a malicious file (commonly a PHP web shell) with an executable extension
3. The vulnerable component accepts and stores the file without proper validation
4. The attacker accesses the uploaded malicious file via its web-accessible path
5. The web server executes the malicious code, granting the attacker remote code execution capabilities

For technical analysis and additional details, refer to the Binqqer CVE-2024-51053 Analysis or the Vulners Packet Storm Advisory.

Detection Methods for CVE-2024-51053

Indicators of Compromise

• Unexpected files with executable extensions (.php, .phtml, .phar) appearing in upload directories
• Web server access logs showing POST requests to /main/fileupload.php followed by requests to unusual paths in upload directories
• Presence of web shells or suspicious PHP files containing functions like eval(), system(), exec(), or passthru()
• Unusual outbound network connections originating from the web server process

Detection Strategies

• Monitor HTTP POST requests to /main/fileupload.php for suspicious file uploads, particularly those with executable extensions
• Implement file integrity monitoring (FIM) on web-accessible directories to detect unauthorized file additions
• Deploy web application firewall (WAF) rules to block file uploads with dangerous extensions or suspicious content patterns
• Configure SIEM alerts for command execution attempts originating from the web server user context

Monitoring Recommendations

• Enable verbose logging for the web server and monitor for unusual activity patterns around the file upload endpoint
• Implement real-time monitoring of web directories for newly created executable files
• Review web server process activity for spawned shells or unexpected child processes
• Monitor for post-exploitation indicators such as reverse shell connections or data exfiltration attempts

How to Mitigate CVE-2024-51053

Immediate Actions Required

• If possible, disable or restrict access to the /main/fileupload.php endpoint until a patch is available
• Implement network-level access controls to limit who can reach the vulnerable endpoint
• Deploy web application firewall rules to block file uploads with executable extensions
• Audit upload directories for any suspicious or malicious files that may have already been uploaded
• Consider taking the AVSCMS application offline if it is publicly accessible and cannot be adequately protected

Patch Information

At the time of this writing, no official vendor patch has been identified in the available CVE data. Organizations using AVSCMS v8.2.0 should monitor the vendor's official channels for security updates. Consider upgrading to a newer version if one becomes available that addresses this vulnerability.

Workarounds

• Implement strict file extension allowlisting at the web server level, permitting only non-executable file types in upload directories
• Configure the web server to prevent script execution in upload directories using directives such as php_flag engine off for Apache or equivalent settings for other servers
• Use .htaccess or server configuration to deny direct access to uploaded files, serving them through a controlled handler instead
• Implement additional authentication requirements for the file upload functionality
• Consider using a reverse proxy or WAF to inspect and filter malicious upload attempts

# Apache configuration to disable PHP execution in uploads directory
<Directory "/path/to/avscms/uploads">
    php_flag engine off
    <FilesMatch "\.(php|phtml|phar)$">
        Require all denied
    </FilesMatch>
</Directory>