@nyariv/sandboxjs has host prototype pollution from sandbox via array intermediary (sandbox escape)

Exploitation

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

CVSS

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

EPSS

• CVE-2026-25881: 0.62% estimated exploitation activity in the next 30 days; percentile 49.91 (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 allows sandboxed code to mutate host built-in prototypes by laundering the isGlobal protection flag through array literal intermediaries. When a global prototype reference (e.g., Map.prototype, Set.prototype) is placed into an array and retrieved, the isGlobal taint is stripped, permitting direct prototype mutation from within the sandbox. This results in persistent host-side prototype pollution and may enable RCE in applications that use polluted properties in sensitive sinks (example gadget: execSync(obj.cmd)). Details Root Cause: The sandbox implements a protection mechanism using the isGlobal flag in the Prop class to prevent modification of global objects and their prototypes. However, this taint tracking is lost when values pass through array/object literal creation. Vulnerable Code Path src/executor.ts(L559-L571): Exploitation Flow: Protection Bypass Location src/utils.ts(L380-L385): When the prototype is accessed via array retrieval, the…

Published by the source

10 Feb 2026, 00:24 UTC

Last modified by the source

10 Feb 2026, 03:05 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-ww7g-4gwx-m7wj

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-ww7g-4gwx-m7wj

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-ww7g-4gwx-m7wj

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# Patch Next advisory brief: CVE-2026-25881

Advisory: @nyariv/sandboxjs has host prototype pollution from sandbox via array intermediary (sandbox escape)
IDs: CVE-2026-25881, GHSA-ww7g-4gwx-m7wj
Record: https://patchnext.com/advisories/cve-2026-25881 (revision 3, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @nyariv/sandboxjs 0.8.31. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @nyariv/sandboxjs: affected <= 0.8.30; fixed in 0.8.31

## 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-ww7g-4gwx-m7wj (GitHub-reviewed advisory GHSA-ww7g-4gwx-m7wj lists affected ranges: npm @nyariv/sandboxjs >=0 <=0.8.30)
- Verified: https://osv.dev/vulnerability/GHSA-ww7g-4gwx-m7wj (OSV record GHSA-ww7g-4gwx-m7wj lists affected ranges: npm @nyariv/sandboxjs >=0 <0.8.31 (fixed))

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