CVE-2026-47686

**Affected:** vm2 <= 3.11.3 **CVSS 3.1:** 9.9 HIGH (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) **CWE:** CWE-693 (Protection Mechanism Failure) **Prerequisite:** Embedder exposes a host function that throws an Error with `.cause` referencing a powerful host object (e.g., `process`) ## Summary I found that `handleException()` in `lib/setup-sandbox.js` recursively sanitizes sub-errors for `SuppressedError` and `AggregateError`, but completely ignores the ES2022 `Error.cause` property. When sandbox code catches a host-thrown error carrying a `.cause` that references a host object like `process`, it can traverse that reference to achieve arbitrary command execution on the host. The project's own `docs/ATTACKS.md` (Defense Invariant #3, line 54) explicitly claims Error.cause is sanitized. The implementation does not match this claim. ## Root Cause The `handleException` function (lines 869-959 of `lib/setup-sandbox.js`) walks the prototype chain of caught errors looking for `SuppressedError` and `AggregateError`. When it finds them, it recursively sanitizes their contained errors (`.error`, `.suppressed`, `.errors[]`). For all other error types, it returns `e` directly at line 958 without inspecting `.cause`. ```javascript 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 } ``` Error.cause was introduced in ES2022 (Node 16.9+). When `handleException` was extend