Vulnerability · Published Sep 17, 2026 · Assigned by VulnCheck
CVE-2026-92959vm2 before 3.11.8 allowAsync Bypass via Promise Thenable
High 7.1
In plain English
A high-severity security flaw in vm2 from patriksimek. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | vm2 | 3.11.8 | GHSA-f8gf-w286-fmq2 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| patriksimek | vm2 | 0 – before 3.11.8 |
Weakness: CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
References
- GitHub Security Advisory (GHSA-f8gf-w286-fmq2) vendor-advisory
- VulnCheck Advisory: vm2 before 3.11.8 allowAsync Bypass via Promise Thenable third-party-advisory