CVE-2026-47210: vm2 sandbox escape via JSPI-backed Promise `.finally()` species bypass

Synopsis

This is a sandbox escape vulnerability in vm2, a widely used Node.js sandbox library. A remote attacker can send untrusted JavaScript that uses a JSPI-backed Promise (available when WebAssembly JSPI is exposed by the runtime) to bypass Promise-species hardening inside the vm2 sandbox, reaching attacker-controlled logic with a host-originated rejection object. Successful exploitation gives the attacker full code execution in the host Node.js process, enabling complete confidentiality, integrity, and availability impact. A patched-image rebuild at vm2 version 3.11.4 is available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must be able to reach the service over the network to submit untrusted JavaScript for execution inside the vm2 sandbox.

• AuthenticationNot required

  No credentials or account are needed; the vulnerability is reachable by any unauthenticated caller who can submit code to the sandbox.

• Victim interactionNot required

  Exploitation is fully attacker-driven and requires no action from any user or operator on the target system.

• Attack complexityDetail

  The exploit is reliable and condition-free once the runtime exposes WebAssembly JSPI; no race conditions or special memory layout are required.

Blast Radius

• The attacker executes arbitrary code inside the host Node.js process, escaping all sandbox boundaries.
• All data readable by the host process, including environment variables, secrets, and in-memory application state, is exposed to the attacker.
• The attacker can write or overwrite files, modify application data, and tamper with any resource the host process has write access to.
• The host process can be crashed or held in a tight loop, taking down the Node.js application entirely.