GHSA-8hg8-63c5-gwmx

Summary

When a NodeVM is created with nesting: true, sandbox code can unconditionally require('vm2') regardless of the outer VM's require configuration — including require: false. With access to vm2, the sandbox constructs a new inner NodeVM with its own unrestricted require settings and executes arbitrary OS commands on the host. Any application that runs untrusted code inside a NodeVM with nesting: true is fully compromised.

Details

The vulnerability is in how the nesting: true option interacts with the legacy module resolver.

lib/nodevm.js:96-99 — NESTING_OVERRIDE is a special builtin map that injects the vm2 package into the sandbox:

const NESTING_OVERRIDE = Object.freeze({
  __proto__: null,
  vm2: vm2NestingLoader
});

lib/nodevm.js:268-269 — When nesting: true, this override is passed into the resolver factory alongside the host's require options:

const customResolver = requireOpts instanceof Resolver;
const resolver = customResolver ? requireOpts : makeResolverFromLegacyOptions(
  requireOpts,
  nesting && NESTING_OVERRIDE,  // ← injected when nesting:true
  this._compiler
);

lib/resolver-compat.js:193-197 — This is the vulnerable branch. When require: false is set, requireOpts is falsy, so !options is true. Without nesting the function returns DENY_RESOLVER (block everything). With nesting, it instead builds a resolver that includes vm2 from NESTING_OVERRIDE:

function makeResolverFromLegacyOptions(options, override, compiler) {
  if (!options) {
    if (!override) return DENY_RESOLVER;  // require:false, no nesting → deny all
    // BUG: require:false + nesting:true reaches here
    // override (NESTING_OVERRIDE) is applied, making vm2 available
    const builtins = makeBuiltinsFromLegacyOptions(undefined, defaultRequire, undefined, override);
    return new Resolver(DEFAULT_FS, [], builtins);  // vm2 is now requireable
  }
  // ...
}
```...