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SandboxjsApplication · Nyariv

CVE-2026-26954

CRITICAL · 10.0 CVSS v3.1 Published 2026-03-13
Fix available
A fix is available. Upgrade to 0.8.34 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click

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 0.8.34, it is possible to obtain arrays containing Function, which allows escaping the sandbox. Given an array containing Function, and Object.fromEntries, it is possible to construct {[p]: Function} where p is any constructible property. This vulnerability is fixed in 0.8.34.

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 0.8.34 contain a sandbox escape vulnerability where arrays containing Function objects can be combined with Object.fromEntries to construct {[p]: Function}, allowing attackers to access constructible properties and escape sandbox restrictions.

MitigationUpgrade SandboxJS to version 0.8.34 or later to remediate this critical sandbox escape vulnerability.

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:< 0.8.34

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. Check installed SandboxJS version
    Run 'npm list sandboxjs' or check package.json dependencies to find the installed version of sandboxjs
    Affected if The installed version is lower than 0.8.34
  2. Verify package name
    Confirm the package is named 'sandboxjs' or 'nyariv-sandboxjs' in your dependencies
    Affected if The package name matches either sandboxjs or nyariv-sandboxjs and version is below 0.8.34
  3. Search for Object.fromEntries usage with Function arrays
    Search codebase for patterns like 'Object.fromEntries' combined with arrays that may contain Function objects, such as Object.fromEntries([...functions]) or similar constructions
    Affected if Code uses Object.fromEntries with arrays containing Function objects in a sandbox context
  4. Inspect sandbox configuration
    Review sandbox configuration to determine if the sandbox allows access to Object.fromEntries or Function constructor
    Affected if The sandbox permits access to Object.fromEntries or enables Function object construction that could be combined with Object.fromEntries
  5. Test for constructible property access
    Evaluate whether code within the sandbox can access constructible properties like Object.prototype.constructor or spawn new Function instances
    Affected if Sandboxed code can access constructor properties or create new Function objects which combined with Object.fromEntries enables the escape

User is affected if SandboxJS version is below 0.8.34 and the sandbox environment allows Object.fromEntries usage with Function objects that could be combined to escape restrictions.

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 0.8.34 or later
Fixed in 0.8.34
Interim mitigation

Upgrade SandboxJS to version 0.8.34 or later to remediate this critical sandbox escape vulnerability.

Recommended fix High confidence

0.8.34

  1. Check the current version of sandboxjs in your project by reviewing package.json or running npm list sandboxjs
  2. Update sandboxjs to version 0.8.34 or later using your package manager (e.g., npm install [email protected] or npm update sandboxjs)
  3. Verify the update was successful by checking the installed version
  4. Test your application's sandbox functionality to ensure the security fix does not break expected behavior
  5. Rebuild and redeploy any services that depend on sandboxjs
Caveat Review the changelog between your current version and 0.8.34 to check for any breaking changes in sandbox behavior

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

Fix this in Sandboxjs Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

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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-2026-26954 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