dbcve.org
Code InjectionWeakness · CWE-94

CVE-2026-55388

HIGH · 8.1 CVSS v3.1 Published 2026-06-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
90/100
Remediation priority · Urgent
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
piscina is a node.js worker pool implementation. Prior to 6.0.0-rc.2, 5.2.0, and 4.9.3, piscina's constructor and run() paths read the filename option via plain member access. Both reads fall through the prototype chain when the caller's options object doesn't have filename as an own property. When Object.prototype.filename is polluted upstream the inherited value flows to worker_threads.Worker import and the attacker's .mjs runs in the worker. This vulnerability is fixed in 6.0.0-rc.2, 5.2.0, and 4.9.3.

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

This is a prototype pollution vulnerability in piscina's worker pool implementation. The filename option is read via plain member access without checking if it exists as an own property on the options object. When Object.prototype.filename is polluted upstream, the inherited value flows to worker_threads.Worker, causing arbitrary .mjs files to execute in the worker context, leading to remote code execution.

MitigationUpgrade to piscina version 6.0.0-rc.2, 5.2.0, or 4.9.3 or later, which includes the fix using hasOwnProperty checks for the filename option.

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

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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 if piscina is installed in the project
    Run 'npm list piscina' or inspect package.json dependencies to see if piscina is listed as a dependency
    Affected if piscina is not present in dependencies (not vulnerable if not used)
  2. Determine installed piscina version
    Run 'npm list piscina' to see the exact version number, or check node_modules/piscina/package.json for the version field
    Affected if Version is less than 4.9.3, OR between 4.9.3 and 5.2.0, OR between 5.2.0 and 6.0.0-rc.2 (all vulnerable versions)
  3. Inspect worker pool configuration for filename option usage
    Search codebase for Piscina instantiation where 'filename' is passed as an option, or review any dynamic options passed to the worker pool
    Affected if The filename option is explicitly set or options are passed from untrusted sources to the worker pool configuration
  4. Check for prototype pollution vulnerability in the application
    Audit code paths where user-controlled data is merged into objects without proper checks, specifically looking for Object.assign or spread operator usage on configuration objects
    Affected if Object.prototype can be polluted with a 'filename' property containing a path to a malicious .mjs file
  5. Verify worker_threads module is accessible to piscina
    Confirm the application uses worker_threads (piscina relies on Node.js worker_threads module) and check if the process can load arbitrary .mjs files from controllable paths
    Affected if The application environment allows loading .mjs files from paths an attacker could control

You are affected if your project uses a vulnerable piscina version (below 4.9.3, or between 4.9.3-5.2.0, or between 5.2.0-6.0.0-rc.2) AND the filename option is used in worker pool configuration AND Object.prototype can be polluted upstream with a custom filename value leading to arbitrary .mjs execution.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to piscina version 6.0.0-rc.2, 5.2.0, or 4.9.3 or later, which includes the fix using hasOwnProperty checks for the filename option.

Recommended fix High confidence

Upgrade to piscina version 5.2.0 (or 4.9.3 for 4.x branch, or 6.0.0-rc.2 for 6.x release candidate)

  1. Identify the currently installed piscina version in your project by running `npm list piscina` or checking package.json
  2. Upgrade piscina to version 5.2.0 (or 4.9.3 if staying on the 4.x branch, or 6.0.0-rc.2 if adopting the release candidate) by running `npm install [email protected]`
  3. Verify the upgrade was successful by running `npm list piscina`
  4. Test your application to ensure the worker pool functionality still works correctly after the upgrade
  5. Regenerate your lockfile if needed by running `npm install` to lock the updated version
Caveat Review the changelog between your current version and 5.2.0 for any breaking changes in worker pool behavior or API

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

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing4.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,360
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-55388 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-55388 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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