CVE-2025-52921: Innoshop RCE Vulnerability

CVE-2025-52921 Overview

A critical unrestricted file upload vulnerability exists in Innoshop through version 0.4.1 that allows authenticated attackers to achieve remote code execution on the server. The vulnerability resides in the File Manager functions within the admin panel, where an attacker can upload a seemingly benign image file and subsequently rename it to have a .php extension using the Rename Function. This bypasses the initial file type validation, enabling arbitrary PHP code execution on the target server.

Critical Impact

Authenticated attackers can gain full server-side code execution by exploiting inadequate server-side validation in the File Manager, potentially leading to complete server compromise, data exfiltration, and lateral movement within the network.

Affected Products

• Innoshop versions through 0.4.1
• Innoshop Admin Panel File Manager component
• Systems running Innoshop with administrator-level access

Discovery Timeline

• 2025-06-23 - CVE-2025-52921 published to NVD
• 2025-06-23 - Last updated in NVD database

Technical Details for CVE-2025-52921

Vulnerability Analysis

This vulnerability is classified under CWE-420 (Unprotected Alternate Channel), where the application fails to properly protect an alternate channel that could be used to bypass security controls. The core issue stems from the application's reliance on frontend (client-side) validation to prevent administrators from changing uploaded file extensions to executable formats like .php.

The File Manager initially validates that uploaded files are images, which provides a false sense of security. However, the rename functionality lacks equivalent server-side validation, creating a critical security gap. Once an attacker uploads a malicious PHP file disguised as an image (or simply uploads a legitimate image containing embedded PHP code), they can use the rename function to change the extension to .php, effectively weaponizing the file.

Root Cause

The root cause of this vulnerability is the absence of server-side validation for file extension changes during the rename operation. The application implements file type validation only during the initial upload process, trusting that client-side JavaScript restrictions will prevent administrators from renaming files to dangerous extensions. This security-by-obscurity approach fails because client-side controls can be trivially bypassed using proxy tools or by directly crafting HTTP requests.

Attack Vector

The attack is conducted over the network and requires low-privilege authentication (administrator access to the admin panel). The attacker exploits the vulnerability through the following mechanism:

1. The attacker authenticates to the Innoshop admin panel with valid administrator credentials
2. Using the File Manager, they upload a file containing malicious PHP code, disguising it with an image extension (e.g., shell.jpg) or embedding PHP code within a valid image file
3. The initial upload passes validation since the file appears to be an image
4. The attacker uses an interception proxy like BurpSuite to capture the rename request
5. By modifying the request, they rename the file from shell.jpg to shell.php, bypassing the frontend JavaScript validation that would normally prevent this action
6. A simple GET request to the renamed file (e.g., /path/to/uploads/shell.php) triggers the execution of the embedded PHP code
7. The attacker now has arbitrary code execution capabilities on the server

This attack requires authenticated access but results in a scope change, as compromising the web application can lead to broader server and potentially infrastructure-level compromise.

Detection Methods for CVE-2025-52921

Indicators of Compromise

• Presence of unexpected .php files in upload directories that were previously named with image extensions
• Web server logs showing rename operations followed by direct requests to PHP files in upload directories
• Unusual file modification timestamps in the File Manager upload paths
• Network traffic to known malicious PHP webshell signatures

Detection Strategies

• Monitor web server access logs for GET/POST requests to PHP files within upload directories
• Implement file integrity monitoring (FIM) on upload directories to detect extension changes from image types to executable formats
• Configure web application firewalls (WAF) to alert on requests containing common webshell patterns or suspicious PHP function calls
• Review admin panel audit logs for unusual File Manager activity, particularly rename operations

Monitoring Recommendations

• Enable detailed logging for all File Manager operations including uploads, renames, and deletions
• Set up alerts for any file extension changes from non-executable to executable types in monitored directories
• Deploy endpoint detection and response (EDR) solutions to monitor for suspicious process spawning from web server processes
• Implement network-based detection for outbound connections originating from the web server that could indicate a reverse shell

How to Mitigate CVE-2025-52921

Immediate Actions Required

• Restrict access to the Innoshop admin panel to trusted IP addresses only using firewall rules or .htaccess directives
• Audit existing files in upload directories and remove any unexpected .php files
• Review administrator accounts and revoke access for any unnecessary or suspicious users
• Consider disabling the File Manager rename functionality until a patch is available

Patch Information

As of the last modification date, no official vendor patch has been released for this vulnerability. Organizations should monitor the InnoShop GitHub repository for security updates and patches. For additional technical details about this and related vulnerabilities in Innoshop, refer to the security research blog post.

Workarounds

• Implement server-side validation for all file rename operations to prevent changes to executable extensions
• Configure the web server to prevent PHP execution in upload directories using directives like php_flag engine off in Apache or equivalent configurations
• Deploy a web application firewall (WAF) rule to block rename requests that attempt to change file extensions to .php, .phtml, or other executable formats
• Consider implementing additional authentication layers such as multi-factor authentication (MFA) for admin panel access

# Apache configuration to disable PHP execution in upload directories
# Add to .htaccess in the uploads directory or virtual host configuration
<Directory "/path/to/innoshop/uploads">
    php_flag engine off
    <FilesMatch "\.php$">
        Require all denied
    </FilesMatch>
</Directory>