---
title: "CVE-2026-26954: SandboxJS affected by a Sandbox Escape"
url: https://erroneo.us/security/cve/CVE-2026-26954/
description: "CVE-2026-26954 (@nyariv/sandboxjs (npm)): SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-13
date_modified: 2026-03-16
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-26954"
kev: false
cvss: 10
epss: 0.00619
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-26954: SandboxJS affected by a 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?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). 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) <= 0.8.33, fixed in 0.8.34 . Check your lockfile, including transitive dependencies.

## What it is

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

## Affected packages

- npm `@nyariv/sandboxjs` <= 0.8.33 → fixed: 0.8.34

## Affected products (CVE record)

- nyariv SandboxJS: < 0.8.34

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 10.0 `CVSS:3.1/AV:N/AC:L/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 poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.62% probability of exploitation activity in the next 30 days; percentile 49.

## Sources

- [GitHub Advisory GHSA-6r9f-759j-hjgv](https://github.com/advisories/GHSA-6r9f-759j-hjgv)
- [CVE.org record CVE-2026-26954](https://www.cve.org/CVERecord?id=CVE-2026-26954)
- [NVD entry CVE-2026-26954](https://nvd.nist.gov/vuln/detail/CVE-2026-26954)
- [github.com](https://github.com/nyariv/SandboxJS/security/advisories/GHSA-6r9f-759j-hjgv)
- [github.com](https://github.com/nyariv/SandboxJS/commit/e01505b1ea49f4f13956cd12b7ce01b83d2ee085)
- [github.com](https://github.com/nyariv/SandboxJS/releases/tag/v0.8.34)

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Source page: https://erroneo.us/security/cve/CVE-2026-26954/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt