CVE-2026-92959
vm2: `allowAsync: false` can be bypassed through Promise thenable assimilation in VM and NodeVM
Impact
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
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | vm2 | <= 3.11.7 | 3.11.8 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-f8gf-w286-fmq2
- https://github.com/patriksimek/vm2/security/advisories/GHSA-f8gf-w286-fmq2
- https://nvd.nist.gov/vuln/detail/CVE-2026-92959
- https://github.com/patriksimek/vm2/commit/1d1aa437a5a39b00b3de0deb3e31f751d4884f5f
- https://github.com/patriksimek/vm2/releases/tag/v3.11.8
- https://www.vulncheck.com/advisories/vm2-before-3.11.8-allowasync-bypass-via-promise-thenable