CVE-2025-59528

Comprehensive Technical Analysis of CVE-2025-59528

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2025-59528

Description: Flowise, a drag-and-drop user interface for building customized large language model flows, is vulnerable to remote code execution (RCE) in version 3.0.5. The vulnerability resides in the CustomMCP node, which allows users to input configuration settings for connecting to an external MCP server. The issue arises from the lack of security validation when parsing the user-provided mcpServerConfig string, leading to the execution of arbitrary JavaScript code with full Node.js runtime privileges.

CVSS Score: 10

Severity Evaluation:

• Critical: The CVSS score of 10 indicates a critical vulnerability. The ability to execute arbitrary JavaScript code with full Node.js runtime privileges poses a significant risk, as it can lead to complete system compromise.
• Impact: This vulnerability can result in unauthorized access, data breaches, and system manipulation, including the execution of malicious code.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• User Input Manipulation: An attacker can exploit this vulnerability by crafting a malicious mcpServerConfig string that includes JavaScript code.
• Remote Code Execution: The malicious code can be executed with full Node.js runtime privileges, allowing the attacker to perform various actions such as reading/writing files, executing system commands, and accessing sensitive information.

Exploitation Methods:

• Direct Code Injection: The attacker can inject JavaScript code directly into the mcpServerConfig string, which will be executed by the Function() constructor.
• Payload Delivery: The attacker can deliver payloads that exploit the vulnerability to gain control over the system, exfiltrate data, or perform other malicious activities.

3. Affected Systems and Software Versions

Affected Software:

• Flowise version 3.0.5

Affected Systems:

• Any system running Flowise version 3.0.5, including servers and workstations where the software is deployed.

4. Recommended Mitigation Strategies

Immediate Actions:

• Upgrade to the Patched Version: Upgrade to Flowise version 3.0.6 or later, which includes the patch for this vulnerability.
• Disable Affected Node: Temporarily disable the CustomMCP node until the system can be updated.

Long-Term Mitigations:

• Input Validation: Implement robust input validation and sanitization mechanisms to prevent the execution of arbitrary code.
• Least Privilege Principle: Ensure that the application runs with the least privileges necessary to minimize the impact of potential vulnerabilities.
• Regular Security Audits: Conduct regular security audits and code reviews to identify and mitigate similar vulnerabilities.

5. Impact on Cybersecurity Landscape

Broader Implications:

• Supply Chain Security: This vulnerability highlights the importance of securing third-party components and libraries used in software development.
• Code Execution Risks: It underscores the risks associated with executing user-provided code without proper validation, a common issue in many applications.
• Patch Management: Emphasizes the critical role of timely patch management in maintaining the security of software systems.

6. Technical Details for Security Professionals

Vulnerable Code:

• The vulnerability is located in the convertToValidJSONString function within the CustomMCP.ts file.
• The Function() constructor is used to evaluate and execute user input as JavaScript code.

Example of Vulnerable Code:

function convertToValidJSONString(input) {
    return new Function('return ' + input)();
}

Patched Code:

• The patched version ensures that user input is properly validated and sanitized before being executed.

Example of Patched Code:

function convertToValidJSONString(input) {
    // Validate and sanitize input
    const sanitizedInput = sanitizeInput(input);
    return JSON.parse(sanitizedInput);
}

function sanitizeInput(input) {
    // Implement sanitization logic
    return input.replace(/[^a-zA-Z0-9]/g, '');
}

References:

• GitHub Advisory
• Flowise Release 3.0.6

Conclusion: CVE-2025-59528 is a critical vulnerability that underscores the importance of secure coding practices and timely patch management. Organizations should prioritize upgrading to the patched version and implementing robust security measures to mitigate similar risks in the future.