---
title: "CVE-2026-25881: @nyariv/sandboxjs has host prototype pollution from sandbox via array intermediary (sandbox escape)"
url: https://erroneo.us/security/cve/CVE-2026-25881/
description: "CVE-2026-25881 (@nyariv/sandboxjs (npm)): SandboxJS is a JavaScript sandboxing library. Prior to 0.8.31, a sandbox escape vulnerability allows sandboxed…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-09
date_modified: 2026-02-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-25881"
kev: false
cvss: 9.1
epss: 0.0073
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.7% , percentile 54: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 54% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes @nyariv/sandboxjs (npm) <= 0.8.30, fixed in 0.8.31 . Check your lockfile, including transitive dependencies.

## What it is

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.

## Affected packages

- npm `@nyariv/sandboxjs` <= 0.8.30 → fixed: 0.8.31

## Affected products (CVE record)

- nyariv SandboxJS: < 0.8.31

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.0 `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.73% probability of exploitation activity in the next 30 days; percentile 54.

## Sources

- [GitHub Advisory GHSA-ww7g-4gwx-m7wj](https://github.com/advisories/GHSA-ww7g-4gwx-m7wj)
- [CVE.org record CVE-2026-25881](https://www.cve.org/CVERecord?id=CVE-2026-25881)
- [NVD entry CVE-2026-25881](https://nvd.nist.gov/vuln/detail/CVE-2026-25881)
- [github.com](https://github.com/nyariv/SandboxJS/security/advisories/GHSA-ww7g-4gwx-m7wj)
- [github.com](https://github.com/nyariv/SandboxJS/commit/f369f8db26649f212a6a9a2e7a1624cb2f705b53)

---
Source page: https://erroneo.us/security/cve/CVE-2026-25881/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt