CVE-2025-66802: Contact Tracing System RCE Vulnerability

CVE-2025-66802 Overview

Sourcecodester Covid-19 Contact Tracing System 1.0 contains a critical Remote Code Execution (RCE) vulnerability. The application fails to properly validate file uploads in the user image functionality, allowing attackers to upload a malicious PHP reverse shell that enables complete remote code execution on the target system.

Critical Impact

This vulnerability allows unauthenticated attackers to execute arbitrary code on the server through malicious PHP file uploads, potentially leading to complete system compromise.

Affected Products

• Sourcecodester Covid-19 Contact Tracing System 1.0

Discovery Timeline

• 2026-01-12 - CVE CVE-2025-66802 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-66802

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type). The Sourcecodester Covid-19 Contact Tracing System fails to implement proper file type validation on user profile image uploads. This fundamental security flaw allows attackers to bypass intended restrictions and upload executable PHP files instead of legitimate image files.

The vulnerability exists in the image upload functionality designed for user profile management. When a user uploads a profile image, the application does not adequately verify that the uploaded file is actually an image. An attacker can craft a PHP reverse shell payload, disguise it with an image-like filename or manipulate content-type headers, and successfully upload it to the server.

Once the malicious PHP file is uploaded and stored on the web server, the attacker can access the file directly through a web request, triggering execution of the embedded PHP code. This enables establishment of a reverse shell connection back to the attacker's system, granting full remote access to the compromised server.

Root Cause

The root cause of this vulnerability is the absence of proper server-side file validation in the image upload functionality. The application relies on client-side validation or superficial checks (such as file extension verification) that can be easily bypassed. Proper validation should include:

• MIME type verification using server-side file content inspection
• File extension allowlisting with strict enforcement
• File content analysis to verify actual image data
• Renaming uploaded files to prevent direct execution

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Accessing the user profile or image upload functionality of the Covid-19 Contact Tracing System
2. Crafting a PHP reverse shell payload with appropriate headers to bypass basic validation
3. Uploading the malicious PHP file through the image upload endpoint
4. Locating the uploaded file path on the web server
5. Sending a request to the uploaded PHP file to trigger code execution
6. Establishing a reverse shell connection for persistent access

The vulnerability allows complete compromise of the web server, including access to sensitive contact tracing data, database credentials, and potential lateral movement within the network.

Detection Methods for CVE-2025-66802

Indicators of Compromise

• Presence of PHP files in image upload directories (e.g., files with .php extension in /uploads/ or /images/ folders)
• Unusual outbound network connections originating from the web server process
• Web server logs showing requests to PHP files in image upload directories
• Unexpected shell processes spawned by the web server user account

Detection Strategies

• Monitor file uploads for PHP file signatures and executable content within image directories
• Implement web application firewall (WAF) rules to detect PHP code patterns in file upload requests
• Configure intrusion detection systems to alert on reverse shell connection patterns
• Review web server logs for suspicious access patterns to upload directories

Monitoring Recommendations

• Enable file integrity monitoring on web server upload directories
• Configure alerts for new executable files created in image storage locations
• Monitor network traffic for outbound connections on common reverse shell ports
• Implement logging of all file upload activities with content-type analysis

How to Mitigate CVE-2025-66802

Immediate Actions Required

• Disable or restrict access to the image upload functionality until a patch is applied
• Review upload directories for any existing malicious PHP files and remove them
• Implement server-side file validation using content inspection, not just extension checks
• Configure the web server to prevent PHP execution in upload directories

Patch Information

No official vendor patch information is currently available. Organizations using Sourcecodester Covid-19 Contact Tracing System 1.0 should contact the vendor for security updates or consider implementing the workarounds listed below. Additional technical details can be found in the GitHub PoC Repository.

Workarounds

• Configure .htaccess or web server settings to disable PHP execution in upload directories
• Implement strict file type validation using PHP functions like getimagesize() or finfo_file()
• Store uploaded files outside the web root and serve them through a controlled script
• Rename uploaded files to random strings without preserving the original extension

# Apache configuration to disable PHP execution in uploads directory
# Add to .htaccess file in the uploads directory

# Disable PHP execution in this directory
<FilesMatch "\.php$">
    SetHandler none
    SetHandler default-handler
    Order Allow,Deny
    Deny from all
</FilesMatch>

# Alternative: Disable all script execution
Options -ExecCGI
RemoveHandler .php .phtml .php3 .php4 .php5