CVE-2026-92949: vm2 sandbox bypass via accessor descriptor on frozen objects

CVE-2026-92949 · Severity: medium · CVSS 4 · Published 2026-09-17

vm2 is a Node.js sandboxing library that allows developers to safely execute untrusted JavaScript code in an isolated environment. A vulnerability in versions 3.9.6–3.11.6 allows malicious scripts to bypass the vm.freeze() and vm.readonly() protections—which are meant to prevent modification of critical host objects—by accessing and directly invoking accessor properties (getters/setters) to mutate read-only data. Depending on what host objects are exposed, this could enable attackers to manipulate application state or, in some cases, escalate to host code execution.

Technologies: vm2 (npm). Vendors: npm.

Quick answers

Is CVE-2026-92949 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-92949 being exploited in the wild.
How severe is CVE-2026-92949?
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, SEMVER:introduced=3.9.6,fixed=3.11.7.
Is there a fix for CVE-2026-92949?
Yes. vm2 (npm): upgrade to 3.11.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-92949 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-92949?
Check whether you run vm2 (npm) 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.

How to fix

  • vm2 (npm): upgrade to 3.11.7 or later
    npm install vm2@3.11.7

Technical details

The vulnerability is a protection mechanism failure (CWE-693) affecting the ReadOnlyHandler proxy in vm2's sandbox implementation. When an embedder freezes a host object containing accessor own-properties using vm.freeze() or vm.readonly(), the proxy fails to intercept calls to Object.getOwnPropertyDescriptor() or __lookupSetter__(), which allow sandboxed code to extract the underlying setter function and invoke it directly via .call(). The setter then executes against the unwrapped raw host object in BaseHandler.apply, bypassing the readonly proxy layer. No special VM options or authentication is required; the only precondition is that the embedder has frozen an object with at least one accessor property. Patch version 3.11.7 and later properly restrict access to accessor descriptors.

Affected products

  • patriksimek vm2 3.9.6 through 3.11.6

Identifiers

  • CVE-2026-92949
  • GHSA-633r-hq9m-c4ff

Timeline

  • 2026-08-24: disclosed: GitHub Security Advisory GHSA-633r-hq9m-c4ff published
  • 2026-08-24: patched: Patch version 3.11.7 released
  • 2026-09-17: advisory: CVE-2026-92949 assigned

References

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