CVE-2025-3403

Executive Summary

CVE-2025-3403 is a problematic information disclosure vulnerability affecting multiple Vivotek NVR models (ND8422P, ND9525P, ND9541P) running firmware versions 2.4.0.204, 3.3.0.104, and 4.2.0.101. The flaw resides in an unknown function of the HTML Form Handler component, leading to the inclusion of sensitive information in source code. An attacker can remotely exploit this vulnerability without authentication, potentially exposing credentials, session tokens, or internal configuration details. The vendor was contacted but did not respond, leaving the vulnerability unpatched. Public exploit details have been disclosed, increasing the risk of active exploitation.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, likely due to incomplete scoring data. Based on the vulnerability characteristics (remote, unauthenticated, low complexity, information disclosure), a reasonable estimated CVSS v3.1 vector would be:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (Base Score: 7.5 - High).
The threat level is High due to the ease of exploitation and potential for sensitive data exposure.

Deep Dive & Mechanics

The vulnerability is triggered by sending a crafted HTTP request to the vulnerable NVR's web interface. The HTML Form Handler component fails to properly sanitize or restrict the inclusion of sensitive data (e.g., hardcoded credentials, internal IPs, or API keys) within the HTML source code returned to the client. This is a classic case of CWE-540 (Inclusion of Sensitive Information in Source Code).

The attack vector is remote and requires no authentication. An attacker can simply view the page source or intercept the HTTP response to extract the leaked information. The exact parameter or endpoint is not publicly detailed, but the exploit has been disclosed, indicating that a proof-of-concept exists.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code likely includes something like:

<!-- Vulnerable: sensitive data embedded in HTML comments or hidden fields -->
<input type="hidden" name="admin_password" value="hardcoded_password123">

A patched version would remove such data from the HTML source or use server-side session management:

<!-- Patched: no sensitive data in source -->
<input type="hidden" name="session_token" value="<%= session.getToken() %>">

Exploitation & Lab Setup

Red Team

1. Reconnaissance: Identify Vivotek NVR models via Shodan dorks or banner grabbing.
2. Exploitation: Send a GET request to the vulnerable endpoint (e.g., /cgi-bin/admin/config.cgi or similar).
3. Data Extraction: View the HTML source code for hardcoded credentials, tokens, or internal network details.

Example curl command:

curl -s http://target-ip/cgi-bin/admin/config.cgi | grep -i "password\|secret\|token"

Blue Team

1. Detection: Monitor for unusual HTTP requests to /cgi-bin/ endpoints from external IPs.
2. Honeypot: Deploy a fake Vivotek NVR to capture exploitation attempts.
3. Response: Block IPs scanning for these endpoints and alert on source code leakage patterns.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /cgi-bin/admin/config.cgi or similar paths.
• File: HTML responses containing password, secret, or token in hidden fields or comments.
• Behavior: Unauthenticated access to administrative CGI endpoints.

Detection Engineering

YARA Rule

rule CVE_2025_3403_Vivotek_Info_Leak {
    meta:
        description = "Detects sensitive information leakage in Vivotek NVR HTML responses"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-3403"
    strings:
        $s1 = "password" nocase
        $s2 = "secret" nocase
        $s3 = "token" nocase
        $s4 = "admin" nocase
    condition:
        any of ($s*) and #s1 > 0
}

Sigma Rule

title: Vivotek NVR Sensitive Information Leakage
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP responses containing sensitive data from Vivotek NVR devices
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: '/cgi-bin/admin/'
        sc-status: 200
        response_body|contains:
            - 'password'
            - 'secret'
            - 'token'
    condition: selection
falsepositives:
    - Legitimate admin access
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-3403 Vivotek NVR Info Leak"; flow:to_server,established; content:"/cgi-bin/admin/"; http_uri; content:"password"; http_server_body; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Restrict access to the NVR web interface to trusted IPs only (firewall rules).
• Short-term: Disable the vulnerable CGI endpoints if not required.
• Long-term: Replace the NVR with a patched alternative or apply vendor-supplied firmware when available.
• Compensating Controls: Use a WAF to block requests containing sensitive patterns in responses.

Valters IT
Securing Digital Frontiers