# CVE-2026-26954: SandboxJS sandbox escape allowing remote code execution

Source: https://junglewise.ai/threats/cve-2026-26954-sandboxjs-sandbox-escape-allowing-remote-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-13. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-26954 · Severity: low · CVSS 3.1 · Published 2026-03-13

SandboxJS is a JavaScript sandbox library used to safely execute untrusted code in isolated environments. A critical vulnerability allows attackers to escape the sandbox and execute arbitrary code on the host system by exploiting improper restrictions on access to built-in JavaScript functions like Object.entries() and Object.values().

Technologies: [@nyariv/sandboxjs (npm)](https://junglewise.ai/threats/technologies/nyariv-sandboxjs), [Nyariv Sandboxjs](https://junglewise.ai/threats/technologies/sandboxjs). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Nyariv](https://junglewise.ai/threats/vendors/nyariv).

## Quick answers

**Is CVE-2026-26954 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-26954 being exploited in the wild.

**How severe is CVE-2026-26954?** Low severity, with a CVSS score of 3.1, published 13 March 2026.

**Which products and versions are affected?** @nyariv/sandboxjs (npm) SEMVER:introduced=0,fixed=0.8.34; Nyariv Sandboxjs <= 0.8.33.

**Is there a fix for CVE-2026-26954?** Yes. @nyariv/sandboxjs (npm): upgrade to 0.8.34 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-26954 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-26954?** Check whether you run @nyariv/sandboxjs (npm) or Nyariv Sandboxjs at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @nyariv/sandboxjs (npm): upgrade to 0.8.34 or later

  ```sh
  npm install @nyariv/sandboxjs@0.8.34
  ```


## Technical details

The vulnerability is a code injection (CWE-94) flaw in SandboxJS's sandbox isolation mechanism. An attacker can obtain arrays containing the Function constructor through methods like Object.entries(this).at(1) or Object.values(this).slice(1, 2), then use Object.fromEntries() to construct objects with arbitrary properties mapped to Function. This allows execution of arbitrary code via promise-based gadget chains (e.g., .finally() with code strings). The attack requires no authentication or user interaction and is network-accessible. The vulnerability affects all versions up to and including 0.8.33 and is patched in version 0.8.34.

## Affected products

- nyariv SandboxJS <= 0.8.33

## Identifiers

- CVE-2026-26954
- GHSA-6r9f-759j-hjgv

## Timeline

- 2026-03-13: disclosed
- 2026-03-13: patched: version 0.8.34

## References

- [https://github.com/nyariv/SandboxJS/security/advisories/GHSA-6r9f-759j-hjgv](https://github.com/nyariv/SandboxJS/security/advisories/GHSA-6r9f-759j-hjgv)

## Related threats

- [nyariv SandboxJS sandbox escape via Function.caller leakage](https://junglewise.ai/threats/cve-2026-43898-nyariv-sandboxjs-sandbox-escape-via-function-caller-leakage)
- [SandboxJS sandbox escape via Prop object leak in new handler](https://junglewise.ai/threats/cve-2026-34217-sandboxjs-sandbox-escape-via-prop-object-leak-in-new-handler)
- [SandboxJS stack overflow via deeply nested expressions](https://junglewise.ai/threats/cve-2026-34211-sandboxjs-stack-overflow-via-deeply-nested-expressions)
- [SandboxJS sandbox integrity escape via constructor manipulation](https://junglewise.ai/threats/cve-2026-34208-nyariv-sandboxjs-sandbox-integrity-escape-via-constructor-bypass)
- [SandboxJS execution-quota bypass in timers](https://junglewise.ai/threats/cve-2026-32723-sandboxjs-execution-quota-bypass-in-timers)