# vm2 NodeVM builtin denylist bypass via fs/promises

Source: https://junglewise.ai/threats/duplicate-advisory-vm2-nodevm-builtin-denylist-bypass-via-fs-promises-d3a51a7c  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-10-01  
License: CC BY 4.0 with a link back

Severity: high · CVSS 8.5 · Published 2026-09-17

vm2 is a JavaScript sandbox library used to isolate and execute untrusted code safely. A flaw in its module filtering allows sandboxed code to access filesystem operations (fs/promises) even when the host explicitly denies fs access, enabling attackers to create and modify files on the host system. This breaks the security boundary that the sandbox is designed to enforce.

Technologies: [vm2 (npm)](https://junglewise.ai/threats/technologies/vm2), [Patriksimek Vm2](https://junglewise.ai/threats/technologies/patriksimek-vm2). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Patriksimek](https://junglewise.ai/threats/vendors/patriksimek).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 8.5, published 17 September 2026.

**Which products and versions are affected?** vm2 (npm) <= 3.11.6; Patriksimek Vm2 <= 3.11.6.

**Is there a fix for This vulnerability?** A patch was published on 2026-08-24: Fixed in version 3.11.7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run vm2 (npm) or Patriksimek Vm2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

NodeVM's builtin denylist uses exact-name matching when filtering modules with negative entries (e.g., '-fs'). This fails to block subpaths like fs/promises and does not consistently handle the node: prefix, allowing require('fs/promises') to bypass restrictions. An attacker with code execution within the sandbox can invoke fs/promises.writeFile() and other filesystem operations to read, write, and manipulate host files despite policy denials.

## Affected products

- Patriksimek vm2 <= 3.11.6

## Timeline

- 2026-08-24: disclosed
- 2026-08-24: patched: Fixed in version 3.11.7

## References

- [https://github.com/patriksimek/vm2/security/advisories/GHSA-6rh5-qq4q-97xh](https://github.com/patriksimek/vm2/security/advisories/GHSA-6rh5-qq4q-97xh)

## Related threats

- [vm2 NodeVM path bypass in custom resolution](https://junglewise.ai/threats/duplicate-advisory-vm2-nodevm-custom-resolution-bypasses-external-path-5d3a7272)
- [vm2 NodeVM zlib buffer pool information disclosure](https://junglewise.ai/threats/duplicate-advisory-vm2-nodevm-zlib-buffers-expose-pooled-host-memory-6007c734)
- [vm2 host Promise rejection denial of service in construct trap](https://junglewise.ai/threats/duplicate-advisory-vm2-host-promise-rejection-from-an-exposed-f7aba6ba)
- [vm2 sandbox escape via Buffer backing-store ownership bypass](https://junglewise.ai/threats/cve-2026-100723-vm2-before-3-12-2-does-not-apply-its-buffer-backing-store)
- [vm2 unhandled Promise rejection in construct trap](https://junglewise.ai/threats/cve-2026-100722-vm2-before-3-12-2-does-not-apply-host-side-promise-rejection)