Critical Vulnerabilities in Sungrow iSolarCloud App and WiNet Firmware: Urgent Remediation Required

The recent CSAF advisory from Sungrow has cast a stark light on a series of critical vulnerabilities affecting its iSolarCloud Android App and WiNet Firmware. The report details multiple security flaws—from improper certificate validation and weak cryptography to authorization bypasses and buffer overflows—that could allow a remote attacker to intercept sensitive communications, gain unauthorized access, and potentially execute arbitrary code. While the advisory is aimed at users of solar energy management solutions, the implications extend far beyond a single ecosystem, serving as a timely reminder to all IT administrators and security professionals—even those responsible for Windows systems integrated into industrial or IoT networks.

Overview of the Vulnerabilities​

At the top of the advisory, Sungrow flags a CVSS v4 score of 9.5, underscoring the severity of the vulnerabilities. The affected products include:

• iSolarCloud Android App: Versions 2.1.6 and prior
• WiNet Firmware: All versions

The vulnerabilities are wide-ranging and include:

• Improper Certificate Validation (CWE-295)
• Use of a Broken or Risky Cryptographic Algorithm (CWE-327)
• Authorization Bypass Through User-Controlled Key (CWE-639)
• Use of Hard-Coded Credentials (CWE-798)
• Use of Hard-Coded Password (CWE-259)
• Stack-Based Buffer Overflows (CWE-121)
• Heap-Based Buffer Overflow (CWE-122)
• Download of Code Without Integrity Check (CWE-494)

In many cases, vulnerabilities have been assigned CVEs such as CVE-2024-50691, CVE-2024-50684, and even as high as CVE-2024-50692, with CVSS v4 scores reaching up to 9.5. In layman’s terms, these scores indicate that an adversary exploiting these flaws could potentially compromise complete system integrity with minimal initial access.
Summary: Multiple high-severity vulnerabilities in Sungrow’s products put critical infrastructure at risk, with CVSS scores as high as 9.5 highlighting the urgent need for remediation.

Deep Dive: The Technical Details​

1. Certificate and Cryptographic Issues​

• Improper Certificate Validation (CWE-295):
  The iSolarCloud Android App explicitly ignores certificate errors. This shortfall paves the way for man-in-the-middle (MitM) attacks, where a malicious actor can impersonate the server and intercept communications.
  Impact: Attackers could eavesdrop on or manipulate information in transit between the app and its back-end services.
• Use of a Broken or Risky Cryptographic Algorithm (CWE-327):
  The app relies on an insecure AES key with insufficient entropy. Consequently, data transmitted between mobile devices and servers may be decrypted by attackers with relative ease.
  Impact: Confidential data could be exposed or tampered with due to weak encryption practices.

Summary: Flaws in both certificate validation and encryption can seriously undermine the trust and confidentiality of communications—a situation that no IT professional can overlook.

2. Authorization Bypass and Hard-Coded Credentials​

• Authorization Bypass (CWE-639):
  Several API endpoints—including those in the powerStationService, userService, orgService, commonService, and devService—are reported to suffer from insecure direct object reference (IDOR) issues. This allows adversaries to manipulate API calls to gain unauthorized access or modify critical data.
  Impact: Unauthorized actions ranging from data viewing to modification could become possible with minimal effort by attackers.
• Hard-Coded Credentials (CWE-798 & CWE-259):
  Two separate issues have been spotlighted:
  • The iSolarCloud Android App and its corresponding cloud service use hard-coded MQTT credentials, while
  • WiNet Firmware contains hardcoded MQTT credentials and even a hard-coded password for decrypting firmware updates.
  The presence of these fixed credentials creates an easy entry point for attackers, who could leverage them to bypass standard authentication protocols and execute arbitrary commands on the devices.
  Impact: With credentials openly embedded in the firmware or app, attackers can impersonate legitimate users or even the device itself, leading to potentially catastrophic breaches.

Summary: Authorization bypasses and the use of hard-coded credentials open a veritable Pandora’s box for attackers—rendering seemingly secure systems alarmingly vulnerable.

3. Buffer Overflows and Update Mechanism Vulnerabilities​

• Stack-Based and Heap-Based Buffer Overflows (CWE-121 & CWE-122):
  Multiple vulnerabilities related to buffer overflows have been identified:
  • Stack-based issues arise when copying data from MQTT messages into fixed-size buffers without proper bounds checking.
  • Heap-based overflows occur due to inadequate limits on the size of incoming MQTT messages.
  These oversights provide attackers with the classic tools for executing arbitrary code remotely.
  Impact: A successful buffer overflow exploitation could lead to full system compromise, granting attackers the ability to run malicious code with elevated privileges.
• Download of Code Without Integrity Check (CWE-494):
  A particularly worrisome vulnerability in the update mechanism allows an attacker to substitute legitimate firmware downloads with malicious ones. The lack of integrity checks means that any maliciously crafted MQTT message could trigger the installation of compromised firmware.
  Impact: Such an exploit could eventually turn connected devices into bots or offer complete control to an external entity.

Summary: The potential for buffer overflows and tampered firmware updates is a severe hazard, especially in devices that form part of critical industrial or IoT environments.

Implications for Windows-Based IT Environments​

Although these vulnerabilities directly affect Sungrow’s solar cloud and firmware solutions, the broader lesson is one that resonates with Windows administrators everywhere. Many modern IT environments are a mosaic of different operating systems and devices, from Windows servers and workstations to Linux-based IoT devices and proprietary embedded systems. A vulnerability in one component can act as a stepping stone for larger, systemic breaches across the enterprise.

Cross-Platform Risks​

• Integrated Systems:
  Organizations that integrate renewable energy management systems with their Windows-based infrastructure should be vigilant. Attackers who exploit flaws in devices like the iSolarCloud App or WiNet Firmware could potentially use them as pivot points into other parts of the network.
• Network Segmentation:
  This advisory underscores the importance of maintaining strict network segmentation and monitoring, especially when dealing with IoT devices that are often overlooked in traditional IT security reviews.
• Patch Management:
  Just as Windows regularly receives security patches and updates to mitigate vulnerabilities, every connected device—from smartphones to firmware-managed hardware—requires timely updates. Administrators should ensure that firmware updates from vendors like Sungrow are prioritized and applied promptly.

Summary: Even if your primary concern is Windows security, the interconnected nature of modern IT systems means that vulnerabilities in any segment can compromise overall network integrity.

Best Practices and Mitigation Strategies​

In light of these alarming vulnerabilities, it’s crucial for both IT administrators and end-users to take proactive measures:

1. Immediate Firmware and Software Updates:
   Ensure that all devices using the iSolarCloud Android App and WiNet Firmware are updated to the latest versions provided by the vendor. If patches have not yet been released, consider isolating the vulnerable devices from the broader network.
2. Enhance Certificate and Cryptographic Practices:
   • Verify that applications properly validate SSL/TLS certificates.
   • Avoid reliance on weak cryptographic parameters and update AES key generation processes to use higher entropy sources.
3. Review API Security:
   • Implement robust authorization checks rather than relying solely on user-controlled keys.
   • Audit API endpoints for potential IDOR issues and secure them with multi-factor authentication where possible.
4. Avoid Hard-Coded Credentials:
   • Replace hard-coded credentials in both software applications and firmware with dynamically generated, securely stored, and frequently updated credentials.
   • Employ secure vaults or key management services for storing sensitive configuration details.
5. Implement Rigorous Input Validation:
   • Integrate strict bounds checking to prevent buffer overflows at both the stack and heap levels.
   • Use secure coding practices to ensure that error handling does not leave exploitable loopholes.
6. Secure the Update Process:
   • Enforce integrity checks and cryptographic signatures on firmware downloads and updates to ensure authenticity.
   • Implement secure channels for firmware distribution to avoid tampering.

Summary: By adopting a multi-layered security posture—from rigorous patch management to hardened API and update mechanisms—administrators can mitigate these vulnerabilities and fortify their networks against similar threats.

Conclusion​

The Sungrow CSAF advisory is a wake-up call for all technology stakeholders involved in managing integrated IT environments—whether powered by Windows or otherwise. The vulnerabilities detailed in the iSolarCloud Android App and WiNet Firmware expose risks that extend beyond isolated devices and into the broader organizational fabric. With scores peaking at 9.5 on the CVSS scale, the urgency for remediation cannot be understated.
Windows administrators, in particular, should take note of these developments. While Microsoft security patches regularly address vulnerabilities within its own ecosystem, the peripheral devices and firmware that interface with Windows environments demand equal scrutiny. Strong, interconnected security policies and coordinated patch management can help ensure that a weakness in one corner does not lead to a full-scale breach.
Stay alert, update your systems, and remember: in today’s interconnected world, a vulnerability in one device can be the proverbial Trojan horse for an attacker looking to compromise your entire network.
Summary: Vigilance and swift remediation are your best defenses. Keep your systems updated, audit your network environments, and apply best practices to maintain robust security in a world where every device—from Windows servers to IoT firmware—can be a potential gateway for attackers.
By staying informed of such vulnerabilities and taking proactive security measures, IT professionals can help safeguard not only their immediate systems but also the broader digital infrastructure that underpins modern enterprise operations.

---

Source: CISA Sungrow iSolarCloud Android App WiNet Firmware | CISA