CVE-2025-7627: Kkfileviewofficeedit RCE Vulnerability

CVE-2025-7627 Overview

A critical unrestricted file upload vulnerability has been discovered in YiJiuSmile kkFileViewOfficeEdit, affecting all versions up to commit 5fbc57c48e8fe6c1b91e0e7995e2d59615f37abd. The vulnerability exists in the fileUpload function within the /fileUpload endpoint, which fails to properly validate uploaded file types. This allows remote attackers with low privileges to upload arbitrary files to the server, potentially leading to remote code execution, system compromise, or other malicious activities.

Critical Impact

Remote attackers can exploit this unrestricted file upload vulnerability to upload malicious files, potentially achieving code execution on the affected server.

Affected Products

• YiJiuSmile kkFileViewOfficeEdit (all versions up to commit 5fbc57c48e8fe6c1b91e0e7995e2d59615f37abd)

Discovery Timeline

• July 14, 2025 - CVE-2025-7627 published to NVD
• November 7, 2025 - Last updated in NVD database

Technical Details for CVE-2025-7627

Vulnerability Analysis

This vulnerability is classified as an unrestricted file upload issue (CWE-434) combined with improper access control (CWE-284). The fileUpload function in the /fileUpload endpoint does not adequately restrict what types of files can be uploaded by authenticated users. Without proper file type validation, extension filtering, or content verification, attackers can bypass intended restrictions and upload files containing executable code or malicious payloads.

The vulnerability can be exploited remotely over the network and requires only low-level privileges to execute. When successfully exploited, attackers may achieve limited impacts to confidentiality, integrity, and availability of the affected system. The public disclosure of this vulnerability through the vendor's GitHub issue tracker increases the risk of exploitation in the wild.

Root Cause

The root cause of this vulnerability is the absence of proper input validation and file type restrictions in the fileUpload function. The application fails to implement necessary security controls including:

• File extension whitelisting or blacklisting
• MIME type verification
• Content inspection to verify file types match their claimed extensions
• Randomization of uploaded file names and storage locations

These missing controls allow attackers to upload files of any type, including web shells, scripts, or other executable content that could be leveraged for further attacks.

Attack Vector

The attack vector is network-based, requiring the attacker to send crafted HTTP requests to the /fileUpload endpoint. An attacker with low-level authentication can manipulate the File parameter to upload arbitrary files to the server. The exploitation process typically involves:

1. Authenticating to the application with minimal privileges
2. Crafting a multipart form request to the /fileUpload endpoint
3. Including a malicious file (such as a web shell or script) in the upload
4. Accessing the uploaded file to trigger execution

The vulnerability was publicly disclosed through a GitHub Issue Discussion, providing potential attackers with information about the vulnerability and its exploitation.

Detection Methods for CVE-2025-7627

Indicators of Compromise

• Unexpected or suspicious files appearing in upload directories, particularly executable files or scripts
• Web server logs showing unusual requests to the /fileUpload endpoint with atypical file extensions
• Presence of web shells or backdoor scripts in application directories
• Unauthorized file modifications or new executable files in web-accessible directories

Detection Strategies

• Monitor HTTP POST requests to /fileUpload for unusual file extensions such as .php, .jsp, .aspx, or .exe
• Implement file integrity monitoring on directories where uploads are stored
• Deploy web application firewalls (WAF) with rules to detect malicious file upload attempts
• Review access logs for patterns indicating exploitation attempts targeting the upload functionality

Monitoring Recommendations

• Enable detailed logging for all file upload operations including file names, sizes, and requesting user information
• Set up alerts for any upload activity involving executable file types or known malicious extensions
• Implement real-time monitoring of upload directories for newly created files
• Correlate authentication logs with upload activity to identify potential abuse by compromised accounts

How to Mitigate CVE-2025-7627

Immediate Actions Required

• Restrict access to the /fileUpload endpoint to only trusted users or administrators until a patch is available
• Implement server-side file type validation using both extension and MIME type checking
• Consider temporarily disabling the file upload functionality if it is not critical to operations
• Monitor the official GitHub repository for updates and patches

Patch Information

YiJiuSmile kkFileViewOfficeEdit uses a rolling release model, meaning no formal versioned patches are available. Users should pull the latest commits from the official repository and verify that proper file upload validation has been implemented. Check the GitHub Issue Discussion for updates from the maintainers regarding fixes.

Workarounds

• Implement a web application firewall (WAF) rule to filter requests to /fileUpload containing dangerous file extensions
• Deploy the application behind a reverse proxy that inspects and sanitizes file upload requests
• Restrict file uploads to a non-executable directory outside of the web root
• Implement strict file extension whitelisting at the web server or application level, allowing only known-safe file types

# Example nginx configuration to restrict file uploads by extension
location /fileUpload {
    # Only allow specific safe file extensions
    if ($request_filename ~* \.(php|jsp|aspx|exe|sh|bat|cmd|ps1)$) {
        return 403;
    }
    
    # Limit request body size for uploads
    client_max_body_size 10M;
    
    # Additional security headers
    add_header X-Content-Type-Options nosniff;
}