CVE-2025-27939: Growatt Cloud Portal Auth Bypass Flaw

CVE-2025-27939 Overview

CVE-2025-27939 is an Insecure Direct Object Reference (IDOR) vulnerability in the Growatt Cloud Portal that allows unauthenticated attackers to change registered email addresses of other users and take over arbitrary accounts. This authorization bypass vulnerability (CWE-639) enables attackers to manipulate user account data without proper access controls, potentially leading to complete account compromise.

Critical Impact

Attackers can exploit this IDOR vulnerability to hijack user accounts by modifying email addresses, gaining unauthorized access to solar energy monitoring systems and potentially sensitive operational data.

Affected Products

• Growatt Cloud Portal (all versions prior to patch)

Discovery Timeline

• 2025-04-15 - CVE-2025-27939 published to NVD
• 2025-11-12 - Last updated in NVD database

Technical Details for CVE-2025-27939

Vulnerability Analysis

This vulnerability represents a classic Authorization Bypass Through User-Controlled Key (CWE-639), commonly known as Insecure Direct Object Reference (IDOR). The Growatt Cloud Portal fails to properly validate whether the requesting user has authorization to modify email address data for the specified account. This allows an attacker to manipulate request parameters to target arbitrary user accounts, ultimately enabling full account takeover through email address modification.

The attack is particularly dangerous in the context of Industrial Control Systems (ICS) because the Growatt Cloud Portal manages solar energy inverters and monitoring systems. Successful exploitation could allow attackers to gain control over energy infrastructure, modify system configurations, or access sensitive operational data.

Root Cause

The root cause of this vulnerability is insufficient authorization checks in the email address modification functionality. The application accepts user-controlled identifiers to specify which account's email should be modified without verifying that the requesting user owns or has permission to modify that account. This missing access control validation allows any unauthenticated attacker to reference and modify other users' account data.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can craft malicious HTTP requests to the Growatt Cloud Portal API endpoints that handle email address changes. By manipulating account identifiers in these requests, the attacker can target any user account in the system.

The attack flow typically involves:

1. Identifying the API endpoint responsible for email address updates
2. Enumerating or guessing valid user account identifiers
3. Submitting requests with modified account identifiers pointing to victim accounts
4. Changing the victim's email address to an attacker-controlled email
5. Using password reset functionality to gain full account access

Detection Methods for CVE-2025-27939

Indicators of Compromise

• Unexpected email address change notifications from Growatt Cloud Portal
• Multiple failed login attempts followed by successful password resets
• API requests attempting to enumerate user account identifiers
• Unusual patterns of email modification requests targeting multiple accounts

Detection Strategies

• Monitor API logs for email address modification requests containing sequential or randomized account identifiers
• Implement alerting on multiple email address changes originating from single IP addresses
• Analyze authentication logs for password reset attempts following email address modifications
• Review access logs for requests with mismatched session tokens and account identifiers

Monitoring Recommendations

• Enable detailed logging for all account modification API endpoints
• Configure SIEM rules to detect IDOR attack patterns such as parameter manipulation
• Monitor for bulk enumeration attempts against user management endpoints
• Establish baseline metrics for email address changes and alert on anomalies

How to Mitigate CVE-2025-27939

Immediate Actions Required

• Review the CISA ICS Advisory ICSA-25-105-04 for official guidance and updates
• Implement additional authentication requirements for sensitive account operations
• Enable email verification for all email address changes
• Consider temporary network segmentation of affected Growatt systems
• Audit recent email address modifications for signs of exploitation

Patch Information

Refer to the CISA ICS Advisory ICSA-25-105-04 for the latest patch information and vendor guidance from Growatt. Organizations should apply vendor-provided updates as soon as they become available and follow CISA's recommended security practices for ICS environments.

Workarounds

• Implement network access controls to restrict access to the Growatt Cloud Portal
• Require multi-factor authentication (MFA) for all user accounts
• Configure email notifications for any account changes to enable rapid detection
• Consider deploying a Web Application Firewall (WAF) with rules to detect IDOR patterns
• Segment ICS networks from general enterprise networks to limit exposure