CVE-2024-50694: Sungrow WiNet-S Buffer Overflow Flaw

CVE-2024-50694 Overview

CVE-2024-50694 is a critical stack-based buffer overflow vulnerability affecting SunGrow WiNet-SV200 solar inverter communication devices. The vulnerability exists in firmware version WiNet-SV200.001.00.P027 and earlier versions, where the device fails to properly validate the bounds of a buffer when copying timestamp data received from MQTT messages. This lack of input validation enables attackers to trigger a stack-based buffer overflow, potentially leading to remote code execution or denial of service on affected devices.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary code or crash affected SunGrow WiNet-SV200 devices by sending specially crafted MQTT messages, potentially disrupting solar energy monitoring and management systems.

Affected Products

• SunGrow WiNet-SV200 Firmware version WiNet-SV200.001.00.P027 and earlier
• SunGrow WiNet-S hardware devices
• SunGrow solar inverter communication modules utilizing affected firmware

Discovery Timeline

• 2025-01-24 - CVE-2024-50694 published to NVD
• 2025-05-29 - Last updated in NVD database

Technical Details for CVE-2024-50694

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a critical memory corruption issue affecting the MQTT message handling component of SunGrow WiNet-SV200 firmware. The vulnerability occurs when the device processes timestamp fields embedded within MQTT protocol messages used for communication between solar inverters and monitoring systems.

When the firmware receives an MQTT message containing a timestamp value, it copies this data into a fixed-size stack buffer without first verifying that the incoming data fits within the allocated memory space. An attacker can exploit this by sending MQTT messages with oversized timestamp payloads that exceed the buffer's capacity, causing data to overflow into adjacent stack memory regions.

The network-accessible nature of this vulnerability is particularly concerning in industrial and critical infrastructure contexts, as solar energy monitoring systems are often connected to local networks or the internet for remote management. Successful exploitation could allow attackers to gain control of the device, disrupt solar energy monitoring, or use the compromised device as a pivot point for further network intrusion.

Root Cause

The root cause of CVE-2024-50694 lies in insufficient bounds checking within the MQTT message parsing routine. The firmware's code responsible for extracting timestamp data from incoming MQTT messages uses a copy operation that does not validate the length of the source data against the destination buffer's capacity. This classic buffer overflow pattern results from the absence of proper input validation, allowing attacker-controlled data to overwrite critical stack structures including return addresses and saved registers.

Attack Vector

The attack vector for this vulnerability is network-based, leveraging the MQTT protocol commonly used in IoT and industrial control systems. An attacker positioned on the same network segment as the vulnerable device, or with remote access if the MQTT service is exposed, can craft malicious MQTT messages containing oversized timestamp payloads. These messages are sent to the device's MQTT listener, where the vulnerable parsing code processes them without adequate validation.

The exploitation process involves:

1. Identifying a vulnerable SunGrow WiNet-SV200 device accepting MQTT connections
2. Crafting an MQTT message with a timestamp field exceeding expected bounds
3. Sending the malicious message to trigger the buffer overflow
4. Overwriting stack memory to achieve code execution or cause a denial of service

The vulnerability does not require authentication, user interaction, or special privileges, making it highly exploitable by any attacker with network access to the target device.

Detection Methods for CVE-2024-50694

Indicators of Compromise

• Unexpected crashes or reboots of SunGrow WiNet-SV200 devices
• Anomalous MQTT traffic patterns with unusually large message payloads targeting the device
• Memory corruption errors or segmentation faults in device logs if available
• Unexpected outbound network connections from the affected device indicating potential compromise

Detection Strategies

• Monitor MQTT traffic for messages with abnormally large timestamp fields or payloads exceeding expected protocol specifications
• Implement network intrusion detection rules to flag oversized MQTT messages directed at SunGrow devices
• Deploy network segmentation to isolate IoT and industrial control devices, limiting attacker access vectors
• Review device logs for signs of instability, crashes, or unexpected behavior following MQTT message processing

Monitoring Recommendations

• Enable logging on network devices to capture MQTT traffic metadata for forensic analysis
• Configure alerts for repeated device crashes or connectivity issues affecting SunGrow WiNet-SV200 units
• Establish baseline network behavior for MQTT communications to detect anomalous traffic patterns
• Perform regular firmware version audits to identify devices running vulnerable firmware versions

How to Mitigate CVE-2024-50694

Immediate Actions Required

• Identify all SunGrow WiNet-SV200 devices in your environment running firmware version WiNet-SV200.001.00.P027 or earlier
• Isolate vulnerable devices from untrusted network segments until patches can be applied
• Review and restrict network access to MQTT services on affected devices using firewall rules
• Monitor affected devices closely for signs of exploitation or abnormal behavior

Patch Information

SunGrow has released a security notice addressing this vulnerability. Organizations should consult the Sungrow Security Notice #5961 for official patch information and updated firmware versions. Apply vendor-provided firmware updates as soon as they become available to remediate this critical vulnerability.

Workarounds

• Implement network segmentation to isolate SunGrow WiNet-SV200 devices from general network traffic and untrusted sources
• Restrict MQTT service access using firewall rules to allow connections only from trusted management systems
• Disable remote MQTT access if not required for operational purposes
• Deploy intrusion prevention systems (IPS) capable of inspecting and filtering MQTT traffic for malicious payloads
• Consider placing affected devices behind a VPN to limit network exposure until patched firmware is deployed