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SandboxjsApplication · Nyariv

CVE-2026-25586

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, a sandbox escape is possible by shadowing hasOwnProperty on a sandbox object, which disables prototype whitelist enforcement in the property-access path. This permits direct access to __proto__ and other blocked prototype properties, enabling host Object.prototype pollution and persistent cross-sandbox impact. 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 before 0.8.29 contain a sandbox escape vulnerability where attackers can shadow the hasOwnProperty method on sandbox objects. This shadowing disables the prototype whitelist enforcement in the property-access path, allowing direct access to __proto__ and other blocked prototype properties. The flaw enables host Object.prototype pollution and creates persistent cross-sandbox impact.

MitigationUpgrade to SandboxJS version 0.8.29 or later to apply the security fix. Review existing sandboxes for any signs of prototype pollution as the CVSS 10 indicates complete compromise.

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. Determine installed SandboxJS version
    Run `npm list sandboxjs` or check package.json dependencies for the sandboxjs version number
    Affected if The installed version is below 0.8.29 (e.g., 0.8.28, 0.8.0, etc.)
  2. Identify sandbox object instantiation
    Search codebase for imports of SandboxJS and instantiation calls such as `new Sandbox()`, `createSandbox()`, or similar sandbox constructor patterns
    Affected if Code creates sandbox instances using affected versions of SandboxJS below 0.8.29
  3. Locate property access on sandboxed objects
    Review sandbox configuration and usage code for patterns where sandbox objects are accessed using bracket notation or dot notation (e.g., `sandbox[key]`, `sandbox.prop`)
    Affected if Sandboxed code accesses object properties through dynamic property access patterns that could trigger the hasOwnProperty check path
  4. Detect hasOwnProperty shadowing attempts
    Review sandboxed user code for assignments to `hasOwnProperty` on sandbox objects or any code that overrides this method (e.g., `sandbox.hasOwnProperty = function(){}`)
    Affected if Any code within the sandbox assigns or overrides the hasOwnProperty method on sandbox objects
  5. Inspect for prototype pollution indicators
    Examine runtime sandbox state or logs for unexpected modifications to Object.prototype, or check if `__proto__`, `constructor`, or other prototype properties are accessible from within the sandbox
    Affected if Prototype properties (__proto__, constructor) are accessible or Object.prototype shows unexpected modifications after sandbox execution

A user is affected if their installed SandboxJS version is below 0.8.29 AND their sandboxes execute code that performs property access on sandbox objects, particularly if hasOwnProperty could be shadowed or prototype properties are accessible.

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 apply the security fix. Review existing sandboxes for any signs of prototype pollution as the CVSS 10 indicates complete compromise.

Recommended fix Moderate confidence

sandboxjs version 0.8.29

  1. 1. Identify all dependencies that include the 'sandboxjs' package in your project
  2. 2. Run 'npm list sandboxjs' or check your package.json to confirm the current version
  3. 3. Update sandboxjs to version 0.8.29 or later using 'npm install [email protected]' or 'npm update sandboxjs'
  4. 4. Test your application thoroughly to ensure the sandbox functionality works correctly after the upgrade
  5. 5. Rebuild and redeploy all affected services
Caveat Review release notes for 0.8.29 to check for any API changes that may affect your implementation

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

Fix this in Sandboxjs Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-25586 in production — separate from our analysis above.

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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