GHSA-8hg8-63c5-gwmx

Описание

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:

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

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:

lib/builtin.js:102-106 — NESTING_OVERRIDE is merged unconditionally into builtins, overriding any user-configured allowlist:

The result: require('vm2') always succeeds inside a NodeVM with nesting: true, regardless of require: false, require: { builtin: [] }, or any other restriction. Once the sandbox has vm2, it creates a new inner NodeVM with whatever require config it chooses — unconstrained by the outer VM — and reaches child_process.

This was introduced in commit 2353ce60 (Feb 8, 2022) and survived a major refactor in commit 9e2b6051 (Apr 8, 2023). The JSDoc for nesting does warn that "scripts can create a NodeVM which can require any host module," but does not document that nesting: true silently defeats require: false, which is the non-obvious part of this interaction.

PoC

Requirements: vm2 installed, Node.js v22.22.1 (also reproduced on earlier versions).

Observed output (confirmed on Node v22.22.1, vm2 commit 8dd0591):

The variant with require: false also works — the outer VM's require setting has no effect:

Narrow builtin allowlists are also bypassed. require: { builtin: ['path'] } still allows require('vm2') when nesting is enabled.

Impact

Who is affected: Any application that runs untrusted or user-supplied code inside a NodeVM with nesting: true. This includes multi-tenant code execution platforms, notebook/REPL services, plugin systems, and CI sandboxing tools that use vm2.

What an attacker can do: Execute arbitrary OS commands as the host process user. From there: read/write files, exfiltrate secrets from the environment, move laterally on the host network, or establish persistence.

Severity: The mental model mismatch is the core danger. A developer who sets require: false to lock down modules, then adds nesting: true to allow child VM creation, will believe the sandbox is restricted. It is not — require: false is silently overridden and the sandbox has unrestricted OS access.

Note: nesting: true must be set by the host. This is not a zero-cooperation escape from a default NodeVM. However, it is not pure misconfiguration either: the implementation defeats a strong and reasonable expectation (require: false should mean deny all), and the existing warning in the docs does not surface the require: false bypass specifically.