CVE-2024-43685

Executive Summary

CVE-2024-43685 is a critical Improper Authentication vulnerability in Microchip TimeProvider 4100 devices, specifically within the login modules. This flaw allows an attacker to perform Session Hijacking, potentially gaining unauthorized access to the device's administrative interface. The vulnerability affects all versions from 1.0 up to, but not including, 2.4.7. As of this report, no public proof-of-concept (PoC) code or exploit is available, and the CVSS score is listed as 0.0 (likely unassigned or placeholder). The EPSS score is 0.0%, indicating low exploitation activity in the wild. However, given the nature of the device (a time server used in critical infrastructure), the risk is elevated.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a hardware appliance.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or unassigned value. Based on the vulnerability description (Session Hijacking via Improper Authentication), a reasonable CVSS v3.1 vector would be:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network (N) – The attack can be launched remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed to initiate the attack.
• User Interaction (UI): None (N) – No user action is required.
• Scope (S): Unchanged (U) – The vulnerability does not affect resources beyond the device.
• Confidentiality (C): High (H) – Session hijacking can expose sensitive data.
• Integrity (I): High (H) – An attacker can modify device configuration.
• Availability (A): High (H) – An attacker could disrupt time synchronization services.

Threat Level: Critical (9.8)

Deep Dive & Mechanics

The vulnerability resides in the login modules of the Microchip TimeProvider 4100. Improper Authentication means the device fails to properly verify the identity of a user or session. In the context of Session Hijacking, this likely involves one of the following:

1. Weak Session Token Generation: The device may generate predictable session tokens (e.g., based on timestamps, IP addresses, or sequential numbers). An attacker could predict or brute-force a valid session token.
2. Session Token Leakage: The device might expose session tokens in URLs, logs, or error messages.
3. Lack of Session Expiration: The device may not properly invalidate sessions after logout or after a period of inactivity.
4. Insecure Transmission: Session tokens might be transmitted over unencrypted HTTP, allowing an attacker on the same network to capture them via Man-in-the-Middle (MitM) attacks.

The attack flow would be:

1. Attacker identifies a TimeProvider 4100 device (e.g., via Shodan).
2. Attacker either captures a valid session token (via MitM) or predicts/generates one.
3. Attacker uses the stolen/predicted token to impersonate an authenticated user.
4. Attacker gains administrative access to the device.

Vulnerable vs. Patched Code

No specific code snippets are available. However, the fix in version 2.4.7 likely addresses the root cause by:

• Implementing cryptographically secure random session token generation.
• Enforcing session expiration and invalidation.
• Transmitting session tokens only over HTTPS.
• Validating session tokens against server-side state.

Vulnerable Code (Conceptual):

# Example of weak session token generation
import time
session_token = str(int(time.time()))  # Predictable

Patched Code (Conceptual):

# Example of secure session token generation
import secrets
session_token = secrets.token_hex(32)  # Cryptographically random

Exploitation & Lab Setup

Red Team

Prerequisites:

• A vulnerable Microchip TimeProvider 4100 (version < 2.4.7).
• Network access to the device (e.g., on the same subnet or via the internet).
• Tools: Burp Suite, Wireshark, Python, curl.

Steps:

1. Reconnaissance: Identify the device using Shodan or network scanning.

   shodan search "Microchip TimeProvider 4100"
   

2. Capture Traffic: Use Wireshark to capture HTTP traffic to/from the device.

   tshark -i eth0 -w capture.pcap host <device_ip>
   

3. Analyze Session Tokens: Look for session tokens in cookies or URLs.

   tshark -r capture.pcap -Y "http.cookie" -T fields -e http.cookie
   

4. Predict Tokens: If tokens are predictable (e.g., based on timestamp), write a script to generate them.

   import requests
   import time
   for i in range(100):
       token = str(int(time.time()) + i)
       cookies = {'session': token}
       r = requests.get('http://<device_ip>/admin', cookies=cookies)
       if 'Dashboard' in r.text:
           print(f"Valid token found: {token}")
           break
   

5. Exploit: Use the valid token to access the admin panel.

Blue Team

Detection:

• Monitor for multiple failed login attempts (brute-force of session tokens).
• Alert on unusual session token patterns (e.g., sequential numbers).
• Detect traffic to/from known TimeProvider 4100 devices on non-standard ports.

Prevention:

• Immediately upgrade to version 2.4.7.
• Restrict network access to the device using firewalls.
• Use VPNs for remote management.
• Enable HTTPS and disable HTTP.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests with sequential or timestamp-based session tokens.
  • Multiple requests to /admin or /login endpoints from the same IP.
  • Unusual outbound connections from the TimeProvider device (e.g., to command-and-control servers).
• Host:
  • Unexpected changes to device configuration (e.g., NTP servers, admin credentials).
  • Log entries showing successful logins from unknown IPs.
  • Presence of new user accounts.
• File:
  • Modified configuration files (e.g., /etc/ntp.conf on the device).
  • Unauthorized scripts or binaries uploaded to the device.

Detection Engineering

YARA Rule

rule CVE_2024_43685_Session_Hijacking {
    meta:
        description = "Detects session hijacking attempts against Microchip TimeProvider 4100"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-43685"
    strings:
        $session_cookie = "session="
        $admin_path = "/admin"
        $login_path = "/login"
    condition:
        any of ($session_cookie) and any of ($admin_path, $login_path)
}

Sigma Rule

title: CVE-2024-43685 - Session Hijacking Attempt on Microchip TimeProvider 4100
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential session hijacking attempts by monitoring for sequential or predictable session tokens.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: microchip_timeprovider
detection:
    selection:
        cs-uri-query|contains: "session="
    condition: selection
falsepositives:
    - Legitimate automated tools
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-43685 - Session Hijacking Attempt"; flow:to_server,established; content:"session="; http_cookie; content:"/admin"; http_uri; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade Firmware: Update all TimeProvider 4100 devices to version 2.4.7 or later.
2. Network Segmentation: Place the device on a separate VLAN with strict firewall rules.
3. Disable HTTP: Ensure only HTTPS is used for management.
4. Change Default Credentials: Immediately change all default usernames and passwords.

Long-Term Measures:

• Implement multi-factor authentication (MFA) for device access.
• Regularly audit logs for suspicious activity.
• Subscribe to Microchip security advisories.
• Conduct penetration testing on critical infrastructure devices.

Workaround (if patching is not possible):

• Restrict access to the device's web interface to trusted IPs only.
• Use a reverse proxy with additional authentication.
• Monitor network traffic for anomalies.

Valters IT