vm2 [![NPM Version][npm-image]][npm-url] [![NPM Downloads][downloads-image]][downloads-url] [![License][license-image]][license-url] [![Known Vulnerabilities][snyk-image]][snyk-url]

vm2 is a sandbox that can run untrusted code with whitelisted Node's built-in modules.

Features

• Runs untrusted code securely in a single process with your code side by side
• Full control over the sandbox's console output
• The sandbox has limited access to the process's methods
• It is possible to require modules (built-in and external) from the sandbox
• You can limit access to certain (or all) built-in modules
• You can securely call methods and exchange data and callbacks between sandboxes
• Is immune to all known methods of attacks
• Transpiler support

How does it work

• It uses the internal VM module to create a secure context.
• It uses Proxies to prevent escaping from the sandbox.
• It overrides the built-in require to control access to modules.

For an in-depth look at vm2’s internals, see the CONTRIBUTING.md file.

What is the difference between Node's vm and vm2?

Try it yourself:

import { runInNewContext } from "node:vm";

runInNewContext('this.constructor.constructor("return process")().exit()');
console.log('Never gets executed.');

import { VM } from 'vm2';

new VM().run('this.constructor.constructor("return process")().exit()');
// Throws ReferenceError: process is not defined

Installation

npm install vm2

Quick Examples

import { VM } from 'vm2';

const vm = new VM();
vm.run(`process.exit()`); // TypeError: process.exit is not a function

import { NodeVM } from 'vm2';

const vm = new NodeVM({
	require: {
		external: true,
		root: './',
	},
});

vm.run(
	`
    var request = require('request');
    request('http://www.google.com', function (error, response, body) {
        console.error(error);
        if (!error && response.statusCode == 200) {
            console.log(body); // Show the HTML for the Google homepage.
        }
    });
`,
	'vm.js',
);

Documentation

• VM
• NodeVM
• VMScript
• Error handling
• Debugging a sandboxed code
• Read-only objects
• Protected objects
• Cross-sandbox relationships
• CLI
• 2.x to 3.x changes
• 1.x and 2.x docs
• Contributing

VM

VM is a simple sandbox to synchronously run untrusted code without the require feature. Only JavaScript built-in objects and Node's Buffer are available. Scheduling functions (setInterval, setTimeout and setImmediate) are not available by default.

Options:

• timeout - Script timeout in milliseconds. WARNING: You might want to use this option together with allowAsync=false. Further, operating on returned objects from the sandbox can run arbitrary code and circumvent the timeout. One should test if the returned object is a primitive with typeof and fully discard it (doing logging or creating error messages with such an object might also run arbitrary code again) in the other case.
• sandbox - VM's global object.
• compiler - javascript (default), typescript, coffeescript or custom compiler function. The library expects you to have compiler pre-installed if the value is set to typescript or coffeescript.
• eval - If set to false any calls to eval or function constructors (Function, GeneratorFunction, etc.) will throw an EvalError (default: true).
• wasm - If set to false any attempt to compile a WebAssembly module will throw a WebAssembly.CompileError (default: true).
• allowAsync - If set to false any attempt to run code using async will throw a VMError (default: true).

IMPORTANT: Timeout is only effective on synchronous code that you run through run. Timeout does NOT work on any method returned by VM. There are some situations when timeout doesn't work - see #244.

import { VM } from 'vm2';

const vm = new VM({
	timeout: 1000,
	allowAsync: false,
	sandbox: {},
});

vm.run('process.exit()'); // throws ReferenceError: process is not defined

You can also retrieve values from VM.

let number = vm.run('1337'); // returns 1337

TIP: See tests for more usage examples.

NodeVM

Unlike VM, NodeVM allows you to require modules in the same way that you would in the regular Node's context.

Options: