vm2 has a sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

Exploitation

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

CVSS

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

EPSS

• CVE-2026-47135: 0.27% estimated exploitation activity in the next 30 days; percentile 18.82 (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 vm2 3.11.2 Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge's set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain. Root Cause 1. Incomplete Symbol.for override (setup-sandbox.js:132-142): Only inspect.custom and rejection are blocked. The following 7 Node.js internal symbols pass through as real cross-realm symbols: - nodejs.util.promisify.custom - nodejs.stream.readable - nodejs.stream.writable - nodejs.stream.duplex - nodejs.stream.transform - nodejs.webstream.isClosedPromise - nodejs.webstream.controllerErrorFunction Note: bridge.js isDangerousCrossRealmSymbol covers promisify.custom on reads, but the Symbol.for override in setup-sandbox does not block it at the source. 2. Missing symbol check in bridge…

Published by the source

29 May 2026, 17:44 UTC

Last modified by the source

12 Jun 2026, 19:45 UTC

Source last checked

26 Oct 2026, 12:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m5q2-4fm3-vfqp

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m5q2-4fm3-vfqp

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# Patch Next advisory brief: CVE-2026-47135

Advisory: vm2 has a sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks
IDs: CVE-2026-47135, GHSA-m5q2-4fm3-vfqp
Record: https://patchnext.com/advisories/cve-2026-47135 (revision 2, source checked 26 Oct 2026, 12:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vm2 3.11.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm vm2: affected <= 3.11.3; fixed in 3.11.4

## 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://osv.dev/vulnerability/GHSA-m5q2-4fm3-vfqp (OSV record GHSA-m5q2-4fm3-vfqp lists affected ranges: npm vm2 >=0 <3.11.4 (fixed))
- Verified: https://github.com/advisories/GHSA-m5q2-4fm3-vfqp (GitHub-reviewed advisory GHSA-m5q2-4fm3-vfqp lists affected ranges: npm vm2 >=0 <=3.11.3)

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