CVE-2025-29756 is a high-severity vulnerability affecting SunGrow's iSolarCloud backend user system, which is used to manage data from connected solar devices. The system employs an MQTT (Message Queuing Telemetry Transport) service to transport data from users' connected devices to their web browsers. The vulnerability arises from insufficient authorization controls on the MQTT server, allowing authenticated users to subscribe to any MQTT topic without restriction. Although the MQTT data is encrypted and credentials are obtained via an API call, an attacker with a valid iSolarCloud account can extract these MQTT credentials and the associated decryption key directly from the browser. Using these credentials, the attacker can subscribe to the wildcard topic '#', effectively receiving all messages from all connected devices across the platform. This leads to a significant breach of confidentiality, as sensitive device data from multiple users can be intercepted. The vulnerability is categorized under CWE-862 (Missing Authorization), indicating a failure to properly restrict access to resources. The CVSS 4.0 score of 8.3 reflects a high severity, with network attack vector, low attack complexity, no user interaction, and partial privileges required (authenticated user). The scope is high, as the attacker can access data beyond their own devices, impacting multiple users. No known exploits are currently reported in the wild, and no patches are listed yet, indicating that mitigation may require vendor action or workarounds.

For European organizations using SunGrow's iSolarCloud platform, this vulnerability poses a serious risk to the confidentiality of operational data from solar energy devices. Attackers could intercept telemetry and operational data from multiple devices, potentially revealing sensitive information about energy production, consumption patterns, and device status. This could lead to privacy violations, competitive intelligence gathering, or facilitate further attacks on energy infrastructure. Given the increasing reliance on renewable energy and smart grid technologies in Europe, such data breaches could undermine trust in energy providers and disrupt energy management. Additionally, unauthorized access to device data could be leveraged for sabotage or manipulation of energy systems, although this vulnerability itself does not provide direct control capabilities. The impact is particularly critical for energy companies, utilities, and large-scale solar farm operators who rely on iSolarCloud for device monitoring and management. Compliance with European data protection regulations (e.g., GDPR) may also be affected due to unauthorized data exposure.

Immediate mitigation steps include restricting access to the MQTT broker by implementing strict topic-level authorization controls, ensuring that users can only subscribe to topics associated with their own devices. SunGrow should urgently develop and deploy patches to enforce these restrictions server-side. Organizations should monitor network traffic for unusual MQTT subscription patterns, especially wildcard subscriptions, and implement anomaly detection to identify potential abuse. Additionally, enforcing multi-factor authentication (MFA) on iSolarCloud accounts can reduce the risk of account compromise. Users should be advised to avoid sharing credentials and to regularly update passwords. Where possible, organizations should segment MQTT traffic and isolate critical device data to limit exposure. Until patches are available, organizations might consider limiting access to the iSolarCloud platform or using alternative monitoring solutions. Regular security audits and penetration testing focused on MQTT services are recommended to identify and remediate similar authorization weaknesses.