CVE-2025-1680

Executive Summary

CVE-2025-1680 is a Host Header Injection vulnerability affecting Moxa Ethernet switches. An attacker with administrative privileges can inject a specially crafted Host header into HTTP requests, enabling redirection, link forgery, or phishing attacks. The vulnerability does not impact the confidentiality, integrity, or availability of the device itself or subsequent systems. No public exploit code or proof-of-concept is available, and no patch has been released by Moxa at this time.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating that no official CVSS vector has been assigned. However, based on the description, the vulnerability requires administrative privileges and does not affect CIA triad of the device. The threat level is considered Low due to the high privilege requirement and lack of direct impact on device security. The primary risk is social engineering or phishing attacks leveraging the Host header injection.

Deep Dive & Mechanics

The vulnerability lies in the web service of Moxa Ethernet switches. When an HTTP request is sent to the device, the web server accepts untrusted data (the Host header) without proper validation. An attacker with administrative access can manipulate the Host header to contain arbitrary values. This can be used to:

• Redirect users to malicious sites.
• Forge links that appear to originate from the legitimate device.
• Facilitate phishing attacks by presenting a trusted hostname.

The attack vector is network-based, requiring the attacker to have administrative privileges on the device. The impact is limited to user interaction and does not compromise the device's core functions.

Vulnerable vs. Patched Code

No specific code snippets are available. The vulnerability is a logic flaw in the HTTP header handling. A patched version would likely include validation of the Host header against a whitelist of allowed values or sanitization to reject invalid characters.

Vulnerable Code (Conceptual):

# Example of vulnerable code that trusts the Host header
def handle_request(request):
    host = request.headers.get('Host')
    # Directly using host in redirect or link generation
    redirect_url = f"http://{host}/login"
    return redirect(redirect_url)

Patched Code (Conceptual):

# Example of patched code with validation
def handle_request(request):
    host = request.headers.get('Host')
    allowed_hosts = ['switch.moxa.com', '192.168.1.1']
    if host not in allowed_hosts:
        host = allowed_hosts[0]  # Default to safe host
    redirect_url = f"http://{host}/login"
    return redirect(redirect_url)

Exploitation & Lab Setup

Red Team

Prerequisites:

• Administrative access to the Moxa switch.
• Network connectivity to the device's web interface.

Exploitation Steps:

1. Intercept an HTTP request to the Moxa switch using a proxy (e.g., Burp Suite).
2. Modify the Host header to a malicious domain, e.g., Host: evil.com.
3. Send the crafted request. The device may use the injected Host header in redirects or links.
4. Use the manipulated response to redirect users or craft phishing links.

Example Request:

GET / HTTP/1.1
Host: evil.com
User-Agent: Mozilla/5.0

Blue Team

Detection:

• Monitor HTTP requests for unusual or unexpected Host headers.
• Look for requests where the Host header does not match the device's IP or expected domain.
• Use network monitoring tools to alert on anomalies.

Mitigation:

• Restrict administrative access to trusted IPs only.
• Implement strict input validation on the Host header at the application level.
• Use a reverse proxy to sanitize headers before they reach the device.

Indicators of Compromise (IOCs)

• HTTP requests with Host headers containing unexpected domains or IPs.
• Log entries showing redirects to external domains from the device.
• Unusual outbound connections from the device to external hosts.

Detection Engineering

YARA Rule

rule CVE_2025_1680_Host_Header_Injection {
    meta:
        description = "Detects HTTP requests with suspicious Host headers targeting Moxa switches"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1680"
    strings:
        $http_get = "GET / HTTP/1.1"
        $host_header = "Host:"
        $suspicious_host = /Host:\s*(?:[a-zA-Z0-9-]+\.)*evil\.com/
    condition:
        $http_get and $host_header and $suspicious_host
}

Sigma Rule

title: CVE-2025-1680 Host Header Injection Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with manipulated Host headers targeting Moxa switches
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: moxa
detection:
    selection:
        cs-host|contains:
            - 'evil.com'
            - 'malicious'
    condition: selection
falsepositives:
    - Legitimate administrative testing
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-1680 - Moxa Host Header Injection Attempt"; flow:to_server; content:"Host:"; nocase; pcre:"/Host:\s*(?:[a-zA-Z0-9-]+\.)*evil\.com/Hi"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

• Restrict administrative access to the device via firewall rules.
• Use a reverse proxy or WAF to validate and sanitize Host headers.
• Monitor logs for unusual Host header values.

Long-term Fix:

• Apply firmware updates from Moxa when available.
• Implement proper input validation in the web service code.
• Conduct regular security assessments of network devices.

Workarounds:

• Disable the web interface if not required.
• Use HTTPS with strict hostname verification.

Valters IT