vm2 before 3.11.8 allowAsync Bypass via Promise Thenable
At a glance
Severity
HIGH 7.1
EPSS
EPSS 0.45 % · percentile 39 (2026-10-27)
State
PUBLISHED
Published
Updated
Assigner
VulnCheck
NVD status
Deferred
Description
vm2 before 3.11.8 does not fully enforce the allowAsync: false option in VM and NodeVM. While localPromise.prototype.then is replaced with a handler that throws 'Async not available', the sandbox's Promise static methods (Promise.resolve, Promise.all, Promise.race, Promise.any, and Promise.allSettled) still assimilate attacker-supplied thenables: native promise resolution performs PromiseResolveThenableJob and invokes the sandboxed code's then method in a microtask without passing through the patched then, so the async restriction is never applied. As a result, sandboxed script can schedule work that runs after VM.run() or NodeVM.run() has returned and outside the configured timeout, continuing to execute after the host believes execution is complete.
