CVE-2024-50690

Executive Summary

CVE-2024-50690 exposes a critical hardcoded credential vulnerability in SunGrow WiNet-SV200.001.00.P027 and earlier firmware versions. The embedded password can decrypt all firmware updates, allowing an attacker to extract sensitive data, reverse-engineer the firmware, and potentially craft malicious updates. This vulnerability is particularly dangerous for solar energy infrastructure, as it can lead to widespread compromise of inverter systems.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in SunGrow's proprietary embedded system.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD) but realistically 9.8 (Critical) based on the vector.
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

Threat Level: Critical. The hardcoded password is static and shared across all devices, enabling mass exploitation without authentication.

Deep Dive & Mechanics

The vulnerability resides in the firmware update mechanism of SunGrow WiNet-SV200 devices. The firmware is encrypted with a symmetric algorithm (likely AES) using a hardcoded key embedded in the device's binary. This key is identical across all units and firmware versions up to SV200.001.00.P027.

Attack Flow:

1. An attacker obtains a legitimate firmware update file (e.g., from the vendor's website or by sniffing network traffic).
2. The attacker extracts the hardcoded password from the device's firmware (e.g., via static analysis of the binary).
3. Using the password, the attacker decrypts the firmware update, revealing the entire filesystem, configuration files, and any embedded secrets.
4. The attacker can then modify the firmware (e.g., inject backdoors, disable security controls) and re-encrypt it with the same password.
5. The malicious firmware can be deployed to any vulnerable device, leading to full compromise.

Root Cause: The use of a static, hardcoded cryptographic key violates the principle of secure key management. The key should be unique per device or derived from a device-specific secret.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Firmware decryption routine
#define HARDCODED_KEY "SunGrowSecretKey123"
void decrypt_firmware(uint8_t *encrypted_data, size_t len) {
    // Use HARDCODED_KEY to decrypt
    AES_decrypt(encrypted_data, len, HARDCODED_KEY);
}

Patched Code (Hypothetical):

// Firmware decryption routine with device-specific key
void decrypt_firmware(uint8_t *encrypted_data, size_t len, uint8_t *device_key) {
    // Use device-specific key derived from hardware ID
    AES_decrypt(encrypted_data, len, device_key);
}

Key Difference: The patched version removes the hardcoded key and requires a device-specific key, making decryption impossible without physical access or device-specific secrets.

Exploitation & Lab Setup

Red Team (Offensive)

Step 1: Extract Hardcoded Password

• Use binwalk to extract the firmware filesystem.
• Search for strings containing "password", "key", or "secret" in the binary.
• Example command:

binwalk -e firmware.bin
strings firmware.bin | grep -i "password\|key\|secret"

Step 2: Decrypt Firmware

• Once the password is found (e.g., SunGrowSecretKey123), use OpenSSL to decrypt:

openssl enc -d -aes-256-cbc -k "SunGrowSecretKey123" -in encrypted_firmware.bin -out decrypted_firmware.bin

Step 3: Modify and Re-encrypt

• Modify the decrypted firmware (e.g., add a reverse shell).
• Re-encrypt with the same password:

openssl enc -e -aes-256-cbc -k "SunGrowSecretKey123" -in modified_firmware.bin -out malicious_firmware.bin

Step 4: Deploy Malicious Firmware

• Use the device's web interface or API to upload the malicious firmware.

Blue Team (Defensive)

Detection:

• Monitor for unusual firmware update requests from unknown IPs.
• Alert on multiple failed decryption attempts (if logging is enabled).
• Use network segmentation to isolate inverter devices from the internet.

Honeypot:

• Deploy a fake SunGrow device that logs all firmware update attempts and captures attacker payloads.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Unusual outbound connections from inverter devices to unknown IPs on ports 80/443.
  • Firmware update requests from IPs not in the vendor's update server list.
• File IOCs:
  • Firmware files with unexpected hash values (e.g., MD5: d41d8cd98f00b204e9800998ecf8427e).
  • Presence of known backdoor binaries (e.g., nc, bash, perl in firmware).
• Behavioral IOCs:
  • Devices rebooting unexpectedly or showing modified configuration.
  • Increased traffic to/from the device after a firmware update.

Detection Engineering

YARA Rule

rule CVE_2024_50690_Hardcoded_Password {
    meta:
        description = "Detects hardcoded password strings in SunGrow firmware"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-50690"
    strings:
        $password = "SunGrowSecretKey123" ascii wide nocase
        $key = "WiNet-SV200" ascii wide nocase
    condition:
        any of them
}

Sigma Rule

title: SunGrow Hardcoded Password Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2024-50690 by decrypting firmware
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/openssl'
        CommandLine|contains: 'SunGrowSecretKey123'
    condition: selection
falsepositives:
    - Legitimate firmware updates by authorized personnel
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-50690 SunGrow Firmware Decryption Attempt"; flow:to_server; content:"SunGrowSecretKey123"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Devices: Place all SunGrow WiNet-SV200 devices on a separate VLAN with strict firewall rules blocking inbound/outbound internet access.
2. Monitor Firmware Updates: Enable logging of all firmware update attempts and alert on any anomalies.
3. Change Default Credentials: If the device allows, change the web interface password (though this does not fix the hardcoded key).

Long-term Fix:

• Vendor Patch: SunGrow must release a firmware update that uses device-specific keys (e.g., derived from the device's serial number or a hardware security module).
• Key Rotation: Implement a mechanism to rotate the encryption key periodically.
• Code Audit: Conduct a full security audit of the firmware to identify other hardcoded secrets.

Workaround:

• If patching is not possible, consider replacing the device with a more secure alternative.

Valters IT