CVE-2026-25881
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 · uneditedSandboxJS is a JavaScript sandboxing library. Prior to 0.8.31, a sandbox escape vulnerability allows sandboxed code to mutate host built-in prototypes by laundering the isGlobal protection flag through array literal intermediaries. When a global prototype reference (e.g., Map.prototype, Set.prototype) is placed into an array and retrieved, the isGlobal taint is stripped, permitting direct prototype mutation from within the sandbox. This results in persistent host-side prototype pollution and may enable RCE in applications that use polluted properties in sensitive sinks (example gadget: execSync(obj.cmd)). This vulnerability is fixed in 0.8.31.
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 confidenceSandboxJS prior to 0.8.31 contains a sandbox escape where placing global prototype references (Map.prototype, Set.prototype) into array literals strips the isGlobal taint flag, allowing sandboxed code to mutate host built-in prototypes. This prototype pollution can reach sensitive sinks like execSync() enabling RCE.
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< 0.8.31CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check installed SandboxJS versionRun 'npm list sandboxjs' or 'npm list' in the project directory to see the installed version. Alternatively, check package.json for the sandboxjs dependency version.Affected if The installed version is lower than 0.8.31 (e.g., 0.8.30, 0.8.0, etc.)
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Identify if sandbox exposes Map or Set prototypesReview the sandbox configuration code to see if Map.prototype, Set.prototype, or other built-in prototypes are exposed to the sandboxed environment. Look for code like 'sandbox.set('Map', Map)' or similar patterns.Affected if Built-in prototypes like Map.prototype, Set.prototype, or WeakMap.prototype are directly exposed to the sandbox without additional protection wrappers.
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Check for sensitive sink usage in sandboxed codeSearch the codebase for usage of dangerous sinks within or alongside sandbox evaluation, particularly child_process.execSync, exec, spawn, or similar commands that could be reached via prototype pollution.Affected if The application uses execSync, exec, or other command execution functions in code that interacts with or could be influenced by the sandboxed environment.
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Verify isGlobal protection is appliedExamine the SandboxJS initialization code to confirm whether isGlobal protection is explicitly enabled for exposed built-in objects. Look for configuration options related to prototype protection.Affected if There is no explicit isGlobal protection configured for exposed built-in prototypes, or the protection can be bypassed via the array literal technique.
You are affected if SandboxJS version is below 0.8.31 AND the sandbox exposes built-in prototypes (Map, Set, etc.) to untrusted code that also has access to sensitive sinks like execSync.
Generated from the published advisory. Verify against your own configuration.
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 · scoped0.8.31
Upgrade to SandboxJS version 0.8.31 or later to patch the isGlobal flag laundering vector.
0.8.31
- Update the Sandboxjs package to version 0.8.31 or later using your package manager (e.g., npm install [email protected] or npm update sandboxjs)
- Verify that the upgrade does not break existing functionality in your application
- Test that the prototype pollution vulnerability is no longer exploitable - confirm that array intermediaries no longer strip the isGlobal taint from global prototype references
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation2.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-25881 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-25881 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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