# vm2 sandbox bypass via accessor descriptor in freeze/readonly

Source: https://junglewise.ai/threats/duplicate-advisory-vm2-vm-freeze-vm-readonly-bypass-via-accessor-c65e1fdb  
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: medium · CVSS 4 · Published 2026-09-17

vm2 is a JavaScript sandbox that allows running untrusted code in isolation. A vulnerability in versions 3.9.6 through 3.11.6 allows attackers to bypass the vm.freeze() and vm.readonly() protections and modify properties that the application explicitly marked read-only. This could enable attackers to alter critical configurations or manipulate host application behavior.

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

## 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?** Medium severity, with a CVSS score of 4, published 17 September 2026.

**Which products and versions are affected?** vm2 (npm) >= 3.9.6, <= 3.11.6; Vm2 3.9.6 to 3.11.6.

**Is there a fix for This vulnerability?** A patch was published on 2026: 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 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

The vulnerability exists in vm2's ReadOnlyHandler, which fails to intercept accessor property descriptors retrieved via Object.getOwnPropertyDescriptor() or __lookupSetter__(). A sandboxed script can extract the host object's setter and invoke it directly, bypassing the readonly proxy wrapper. The attack requires no special VM options; only that the embedder froze an object containing at least one accessor own-property.

## Affected products

- vm2 3.9.6 to 3.11.6

## Timeline

- 2026-08-24: disclosed
- 2026: patched: Fixed in version 3.11.7
- 2026-09-17: advisory

## References

- [https://github.com/patriksimek/vm2/security/advisories/GHSA-633r-hq9m-c4ff](https://github.com/patriksimek/vm2/security/advisories/GHSA-633r-hq9m-c4ff)

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