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SandboxjsApplication · Nyariv

CVE-2026-25520

CRITICAL · 10.0 CVSS v3.1 Published 2026-02-06
Fix available
A fix is available. Upgrade to 0.8.29 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

SandboxJS versions prior to 0.8.29 fail to wrap function return values, allowing attackers to use Object.values/Object.entries to access an Array containing the host's Function constructor, then use Array.prototype.at to retrieve it and execute arbitrary code outside the sandbox - a complete sandbox escape.

MitigationUpgrade to SandboxJS version 0.8.29 or later to obtain the fix that properly wraps function return values.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SandboxjsApplication
Affected:< 0.8.29

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify SandboxJS installation and version
    Check package.json, node_modules/sandboxjs/package.json, or run `npm list sandboxjs` to see the installed version
    Affected if The installed version is any version prior to 0.8.29
  2. Confirm sandbox is executing untrusted code
    Review application code to determine if SandboxJS is used to execute code from untrusted sources (e.g., user-provided scripts, external API inputs)
    Affected if The sandbox processes or evaluates code from untrusted or external sources
  3. Check for direct function return usage
    Inspect the application code that uses SandboxJS to see if functions are being returned from the sandboxed environment to the host
    Affected if The application passes functions from sandboxed code back to the host environment where Object.values/Object.entries could be called on the return values
  4. Verify sandbox isolation configuration
    Review the SandboxJS initialization and configuration to confirm sandboxing is enabled and not running in a privileged mode
    Affected if Sandbox isolation is active and untrusted code execution is occurring (the vulnerability only affects sandboxed environments)

You are affected if SandboxJS version is below 0.8.29 AND your application uses it to run untrusted code that could return functions to the host environment.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.8.29 or later
Fixed in 0.8.29
Vendor patch github.com →
Interim mitigation

Upgrade to SandboxJS version 0.8.29 or later to obtain the fix that properly wraps function return values.

Recommended fix High confidence

0.8.29

  1. Check the current version of sandboxjs in your project by running `npm list sandboxjs` or reviewing package.json
  2. Update sandboxjs to version 0.8.29 or later by running `npm install sandboxjs@^0.8.29` or `npm update sandboxjs`
  3. Verify the installed version matches the requirement: `npm list sandboxjs`
  4. Test that the sandbox functions correctly and that the injection vulnerability is no longer present
  5. Rebuild and redeploy any applications that depend on this package

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Sandboxjs Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
14.0 hours of engineering $2,400
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,840.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-25520 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data