Prototype Pollution in n8n AI Workflow Builder

Executive Summary

This is a prototype pollution vulnerability in n8n versions before 1.123.83, 2.x before 2.41.4, and 2.42.x before 2.42.1. It occurs in the AI workflow builder when merging workflow connections using node names as object members without validating reserved keys. Authenticated users can exploit this by creating nodes named __proto__ via the API and invoking the connect-nodes operation to pollute the global object prototype, which disrupts the instance until a restart.

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Detection Guidance

To detect this vulnerability, check if your n8n instance is running a vulnerable version (before 1.123.83, 2.x before 2.41.4, or 2.42.x before 2.42.1). Inspect API logs for suspicious node creation with names like __proto__. Verify if global object prototype pollution has occurred by testing for unexpected behavior in workflows or system functions.

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Impact Analysis

An attacker with authenticated access could manipulate the prototype chain, leading to unexpected behavior, crashes, or potential code execution. This could disrupt workflows, cause data corruption, or allow unauthorized actions within the n8n instance until the system is restarted.

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Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's safeguards for protected health information. Compliance may be compromised if the vulnerability results in data breaches or unauthorized system changes.

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Mitigation Strategies

Upgrade n8n to a patched version (1.123.83 or later, 2.41.4 or later, or 2.42.1 or later). Review and remove any nodes named __proto__ created by users. Restart the n8n instance to clear any existing prototype pollution effects.

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