CVE-2026-3800: Resort Reservation System RCE Vulnerability

CVE-2026-3800 Overview

A vulnerability has been discovered in SourceCodester/janobe Resort Reservation System 1.0 that allows unrestricted file upload. The vulnerability affects the doInsert function within the /controller.php?action=add endpoint. An attacker can manipulate the image argument to upload arbitrary files, potentially leading to remote code execution. The attack can be executed remotely, and the exploit has been publicly disclosed.

Critical Impact

Unrestricted file upload vulnerabilities can allow attackers to upload malicious web shells or scripts, potentially leading to complete server compromise, data theft, and persistent backdoor access.

Affected Products

• oretnom23 Resort Reservation System 1.0

Discovery Timeline

• 2026-03-09 - CVE-2026-3800 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-3800

Vulnerability Analysis

This vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) and CWE-284 (Improper Access Control). The Resort Reservation System fails to properly validate file uploads through its doInsert function, allowing attackers to bypass intended restrictions on file types.

The vulnerability is network-accessible, meaning remote attackers can exploit it without physical access to the target system. While the vulnerability requires low-privilege authentication, the exploitation itself is straightforward with no user interaction required.

Root Cause

The root cause of this vulnerability lies in insufficient validation of the image parameter in the /controller.php?action=add endpoint. The doInsert function does not properly verify the file type, file extension, or content of uploaded files before storing them on the server. This lack of input sanitization allows attackers to upload files with executable extensions (such as .php) that can then be accessed directly through the web server.

Attack Vector

The attack vector for CVE-2026-3800 is network-based, requiring only authenticated access with low privileges. An attacker can craft a malicious HTTP request to the vulnerable endpoint, submitting a web shell or malicious script disguised as an image file. Once uploaded, the attacker can access the uploaded file directly through the web server to execute arbitrary code.

The exploitation process involves:

1. Authenticating to the Resort Reservation System with low-privilege credentials
2. Crafting a multipart form request to /controller.php?action=add
3. Uploading a malicious PHP file through the image parameter
4. Accessing the uploaded file to execute arbitrary commands on the server

Technical details and proof-of-concept information are available in the GitHub Unrestricted Upload PoC repository.

Detection Methods for CVE-2026-3800

Indicators of Compromise

• Unexpected PHP, ASP, or other executable files in image upload directories
• Web server access logs showing requests to newly uploaded files with suspicious extensions
• Unusual outbound network connections from the web server
• Modified or newly created files with recent timestamps in upload directories

Detection Strategies

• Monitor file system changes in upload directories for non-image file types
• Implement web application firewall (WAF) rules to detect file upload attacks
• Review web server logs for POST requests to /controller.php?action=add followed by GET requests to upload paths
• Use file integrity monitoring to detect unauthorized file additions

Monitoring Recommendations

• Enable detailed logging for the /controller.php endpoint
• Configure alerts for file uploads with executable extensions (.php, .phtml, .asp, etc.)
• Monitor for unusual process spawning from web server processes
• Review authentication logs for suspicious low-privilege account activity

How to Mitigate CVE-2026-3800

Immediate Actions Required

• Restrict access to the Resort Reservation System to trusted networks only
• Disable the file upload functionality until a patch is available
• Implement server-side file type validation using magic bytes, not just file extensions
• Remove any suspicious files from upload directories immediately

Patch Information

No official vendor patch information is currently available for this vulnerability. Organizations using the affected software should monitor the vendor's official channels for security updates. In the meantime, implementing the workarounds below is strongly recommended.

For additional details, refer to VulDB #349767 for tracking information.

Workarounds

• Implement strict file type validation on the server side using MIME type checking and magic byte verification
• Rename uploaded files to random strings and remove executable extensions
• Store uploaded files outside the web root directory
• Configure the web server to disable script execution in upload directories
• Add authentication requirements and rate limiting to the upload endpoint

# Apache configuration to disable PHP execution in upload directory
<Directory "/var/www/html/uploads">
    php_admin_flag engine off
    <FilesMatch "\.(php|phtml|php3|php4|php5|phps)$">
        Require all denied
    </FilesMatch>
</Directory>