SandboxJS has Sandbox Escape via Unprotected AsyncFunction Constructor

Exploitation

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

CVSS

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

EPSS

• CVE-2026-23830: 1.22% estimated exploitation activity in the next 30 days; percentile 68.69 (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 A sandbox escape vulnerability due to AsyncFunction not being isolated in SandboxFunction Details The library attempts to sandbox code execution by replacing the global Function constructor with a safe, sandboxed version (SandboxFunction). This is handled in utils.ts by mapping Function to sandboxFunction within a map used for lookups. However, the library did not include mappings for AsyncFunction, GeneratorFunction, and AsyncGeneratorFunction. These constructors are not global properties but can be accessed via the .constructor property of an instance (e.g., (async () = {}).constructor). In executor.ts, property access is handled. When code running inside the sandbox accesses .constructor on an async function (which the sandbox allows creating), the executor retrieves the property value. Since AsyncFunction was not in the safe-replacement map, the executor returns the actual native host AsyncFunction constructor. Constructors for functions in JavaScript (like Function,…

Published by the source

27 Jan 2026, 19:55 UTC

Last modified by the source

3 Feb 2026, 03:05 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wxhw-j4hc-fmq6

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-wxhw-j4hc-fmq6

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-wxhw-j4hc-fmq6

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# Patch Next advisory brief: CVE-2026-23830

Advisory: SandboxJS has Sandbox Escape via Unprotected AsyncFunction Constructor
IDs: CVE-2026-23830, GHSA-wxhw-j4hc-fmq6
Record: https://patchnext.com/advisories/cve-2026-23830 (revision 3, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 10.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @nyariv/sandboxjs 0.8.26. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @nyariv/sandboxjs: affected < 0.8.26; fixed in 0.8.26

## Suggested inspection (read-only)
- `npm ls @nyariv/sandboxjs --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 @nyariv/sandboxjs.
- 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-wxhw-j4hc-fmq6 (GitHub-reviewed advisory GHSA-wxhw-j4hc-fmq6 lists affected ranges: npm @nyariv/sandboxjs >=0 <0.8.26)
- Verified: https://osv.dev/vulnerability/GHSA-wxhw-j4hc-fmq6 (OSV record GHSA-wxhw-j4hc-fmq6 lists affected ranges: npm @nyariv/sandboxjs >=0 <0.8.26 (fixed))

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