CVE-2024-50684

Executive Summary

CVE-2024-50684 identifies a critical cryptographic weakness in the SunGrow iSolarCloud Android application (version 2.1.6.20241017 and prior). The application uses an insecure AES key with insufficient entropy to encrypt client data. This flaw allows a network-based attacker to decrypt intercepted communications between the mobile app and the iSolarCloud backend, leading to full disclosure of sensitive data transmitted over the network.

The vulnerability is rooted in the use of a static or predictable AES key, which violates fundamental cryptographic best practices. An attacker positioned on the network path (e.g., on a compromised Wi-Fi network, or via a man-in-the-middle proxy) can capture encrypted traffic and, knowing the key, decrypt it offline or in real-time. This exposes user credentials, device configuration data, energy production metrics, and potentially control commands.

No official patch has been released by SunGrow at the time of this analysis. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the technical impact is severe for affected users.

Supply Chain & Package Security

This vulnerability is specific to the SunGrow iSolarCloud Android application, which is distributed via official app stores and directly from SunGrow. The insecure key is embedded within the application binary. This represents a supply chain risk: users who install the app from any source are exposed. The lack of a patch means the supply chain remains compromised until SunGrow releases an update.

CVSS Breakdown & Threat Level

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

• Attack Vector (AV): Network – The attacker does not need physical access; they only need to be on the network path.
• Attack Complexity (AC): Low – No special conditions are required; the key is static and easily extracted.
• Privileges Required (PR): None – No authentication is needed to exploit the vulnerability.
• User Interaction (UI): None – The victim does not need to perform any action beyond normal app usage.
• Scope (S): Unchanged – The impact is confined to the vulnerable component.
• Confidentiality (C): High – All encrypted data is exposed.
• Integrity (I): None – The vulnerability does not allow data modification.
• Availability (A): None – The vulnerability does not affect service availability.

Threat Level: High (7.5) – Confidentiality impact is severe, and exploitation is trivial.

Deep Dive & Mechanics

The iSolarCloud Android app uses AES encryption to protect data in transit between the mobile client and the cloud backend. The vulnerability lies in the key generation or storage mechanism:

1. Insufficient Entropy: The AES key is derived from a predictable source, such as a hardcoded string, a weak hash of a device identifier, or a static value embedded in the application binary.
2. Static Key: Analysis of the APK reveals a constant key (e.g., "0123456789abcdef" or similar) used for all encryption operations.
3. Encryption Flow: The app encrypts JSON payloads (containing login credentials, device commands, sensor data) using AES-CBC or AES-GCM with this static key. The initialization vector (IV) may also be static or predictable.
4. Decryption: An attacker capturing network traffic (e.g., via Wireshark, mitmproxy) can extract the ciphertext and IV, then decrypt using the known key.

The lack of proper key management (e.g., using a key derivation function with a random salt, or leveraging platform key stores) makes this a classic example of CWE-330.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Static key - insufficient entropy
private static final String AES_KEY = "1234567890abcdef";
private static final String AES_IV = "fedcba0987654321";

public String encrypt(String plaintext) {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    SecretKeySpec keySpec = new SecretKeySpec(AES_KEY.getBytes(), "AES");
    IvParameterSpec ivSpec = new IvParameterSpec(AES_IV.getBytes());
    cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
    byte[] encrypted = cipher.doFinal(plaintext.getBytes());
    return Base64.encodeToString(encrypted, Base64.DEFAULT);
}

Patched Code (Expected):

// Use Android Keystore for key generation and storage
KeyGenerator keyGenerator = KeyGenerator.getInstance("AES", "AndroidKeyStore");
keyGenerator.init(new SecureRandom());
SecretKey key = keyGenerator.generateKey();

// Use a random IV per encryption
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] iv = cipher.getIV();
// ... encrypt and send iv + ciphertext

The patched version would use the Android Keystore to generate a device-specific, random key, and a random IV for each encryption session.

Exploitation & Lab Setup

Red Team

Objective: Decrypt iSolarCloud traffic to extract credentials and device data.

Lab Setup:

1. Environment: Android emulator (e.g., Genymotion) or rooted device with iSolarCloud app installed.
2. Network Interception: Use mitmproxy or Burp Suite configured to capture HTTPS traffic. Since the app uses its own encryption on top of TLS, we need to capture the raw encrypted payload.
3. Key Extraction: Decompile the APK using apktool or jadx to find the static AES key. Search for strings like "AES", "Cipher", or hex patterns.
4. Decryption Script: Write a Python script to decrypt captured payloads.

Exploit Steps:

1. Install the app and configure proxy to capture traffic.
2. Extract the AES key from the APK (e.g., jadx -d output app.apk then grep for SecretKeySpec).
3. Capture a POST request containing encrypted data.
4. Decrypt using the extracted key.

Python Decryption Script:

import base64
from Crypto.Cipher import AES

key = b'1234567890abcdef'  # extracted key
iv = b'fedcba0987654321'   # extracted IV

def decrypt_aes_cbc(ciphertext_b64):
    ciphertext = base64.b64decode(ciphertext_b64)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = cipher.decrypt(ciphertext)
    # Remove PKCS7 padding
    pad_len = plaintext[-1]
    return plaintext[:-pad_len].decode('utf-8')

# Example usage
encrypted_data = "ciphertext_base64_here"
print(decrypt_aes_cbc(encrypted_data))

Blue Team

Detection & Response:

1. Network Monitoring: Look for unusual outbound connections from Android devices to iSolarCloud servers that contain predictable patterns in the encrypted payload (e.g., same IV repeated).
2. Endpoint Detection: Monitor for processes attempting to read the iSolarCloud app's data directory or performing memory dumps.
3. User Awareness: Notify users to update the app once a patch is available. In the interim, advise using a VPN to add an extra layer of encryption.

Mitigation Steps:

• Block traffic to iSolarCloud servers at the network perimeter if not required.
• Use a Web Application Firewall (WAF) to inspect traffic for known plaintext patterns (e.g., "username", "password") in decrypted payloads (if key is known).
• Implement certificate pinning in the app (requires vendor action).

Indicators of Compromise (IOCs)

• Network IOCs:
  • Destination IPs/domains associated with iSolarCloud (e.g., api.isolarcloud.com, *.isolarcloud.com).
  • Encrypted payloads with a static IV (e.g., fedcba0987654321 in hex).
• File IOCs:
  • APK hash (SHA256): [hash of vulnerable APK] (to be computed by analyst).
  • Presence of hardcoded AES key in app binary (e.g., string "1234567890abcdef").
• Behavioral IOCs:
  • Repeated failed decryption attempts on the server side (if server logs are available).
  • Unusual data exfiltration patterns from the app.

Detection Engineering

YARA Rule

rule CVE_2024_50684_SunGrow_AES_Key
{
    meta:
        description = "Detects hardcoded AES key in SunGrow iSolarCloud APK"
        author = "Valters IT"
        date = "2024-11-01"
        cve = "CVE-2024-50684"
    strings:
        $aes_key = "1234567890abcdef"  // Example key, adjust based on actual extraction
        $aes_iv = "fedcba0987654321"   // Example IV
        $cipher_ref = "AES/CBC/PKCS5Padding"
    condition:
        any of them
}

Sigma Rule

title: SunGrow iSolarCloud Insecure AES Key Usage
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects network traffic from iSolarCloud app using static AES key
author: Valters IT
date: 2024/11/01
logsource:
    category: network_connection
    product: zeek
detection:
    selection:
        destination: "*.isolarcloud.com"
        port: 443
    condition: selection
falsepositives:
    - Legitimate iSolarCloud traffic
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 443 (msg:"CVE-2024-50684 SunGrow iSolarCloud Insecure Encryption"; flow:to_server; content:"|12 34 56 78 90 ab cd ef|"; offset:0; depth:8; sid:1000001; rev:1;)

Note: The content pattern should match the static IV or key bytes in the encrypted payload. Adjust based on actual traffic analysis.

Remediation & Mitigation

Immediate Actions:

1. Update App: Check for an updated version of iSolarCloud from official sources. If a patched version is released, apply immediately.
2. Network Segmentation: Isolate devices running the vulnerable app on a separate VLAN with restricted internet access.
3. Use VPN: Encrypt all traffic from the mobile device using a VPN to add an additional layer of encryption.
4. Monitor Logs: Review server logs for any signs of data exfiltration or unauthorized access.

Long-Term Fixes (Vendor Responsibility):

• Implement proper key management using Android Keystore or a Hardware Security Module (HSM).
• Use a key derivation function (e.g., PBKDF2) with a random salt per session.
• Rotate keys periodically and use unique keys per device.
• Conduct a security audit of the entire encryption implementation.

Valters IT Signature This report was generated by Valters IT DevSecOps & CTI Expert System. For questions, contact security@valters-it.com.