vm2: vm.freeze()/vm.readonly() bypass via accessor descriptor

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.0 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

EPSS

• CVE-2026-92949: 0.32% estimated exploitation activity in the next 30 days; percentile 24.87 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Untrusted JavaScript running inside new VM().run() / new NodeVM().run() can bypass vm.freeze() / vm.readonly() and mutate a host object the embedder explicitly marked read-only - the documented contract is "prevent sandboxed scripts from adding, changing, or deleting properties". If the frozen host object has an accessor (get/set) own-property, the sandbox can read the host setter back out via Object.getOwnPropertyDescriptor() and call it directly; the call lands in BaseHandler.apply which unwraps the readonly proxy to the raw host object and runs the host setter against it. No non-default VM/NodeVM options are required; the only precondition is that the embedder froze an object whose shape includes an accessor property. A second route to the same sink exists via lookupSetter. PoC Observed output: The first line shows ReadOnlyHandler's documented traps work; the next two show the sandbox mutated the host-side level despite vm.freeze(). Impact A sandboxed script can mutate any…

Published by the source

1 Oct 2026, 15:35 UTC

Last modified by the source

1 Oct 2026, 15:45 UTC

Source last checked

26 Oct 2026, 13:06 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-633r-hq9m-c4ff

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-633r-hq9m-c4ff

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-633r-hq9m-c4ff

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# Patch Next advisory brief: CVE-2026-92949

Advisory: vm2: vm.freeze()/vm.readonly() bypass via accessor descriptor
IDs: CVE-2026-92949, GHSA-633r-hq9m-c4ff
Record: https://patchnext.com/advisories/cve-2026-92949 (revision 3, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vm2 3.11.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm vm2: affected >= 3.9.6, <= 3.11.6; fixed in 3.11.7

## Suggested inspection (read-only)
- `npm ls vm2 --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on vm2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-633r-hq9m-c4ff (GitHub-reviewed advisory GHSA-633r-hq9m-c4ff lists affected ranges: npm vm2 >=3.9.6 <=3.11.6)
- Verified: https://osv.dev/vulnerability/GHSA-633r-hq9m-c4ff (OSV record GHSA-633r-hq9m-c4ff lists affected ranges: npm vm2 >=3.9.6 <3.11.7 (fixed))

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