Skip to content
Patch Next
Sign inAdd to your agent

← Actionable
High, CVSS 8.1amended

piscina: Prototype Pollution Gadget → RCE via inherited options.filename

CVE-2026-55388GHSA-x9g3-xrwr-cwfg

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (piscina 6.0.0-rc.2, 5.2.0, 4.9.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

Add to your agent

Affected packages

  • npm piscina

    Affected
    >= 5.0.0-alpha.0, <= 5.1.4<= 4.9.2>= 6.0.0-rc.1, < 6.0.0-rc.2
    Fixed in
    5.2.0, 6.0.0-rc.2, 4.9.3

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2026-55388: 0.48% estimated exploitation activity in the next 30 days; percentile 41.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary 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 — by any of the well-documented PP-source CVEs (lodash<4.17.13, qs<6.10.3, set-value<4.1.0, minimist<1.2.6, deepmerge<4.2.2, and others) — the inherited value flows to workerthreads.Worker import and the attacker's .mjs runs in the worker. Subtlety: calling pool.run(task) with no second arg uses kDefaultRunOptions which has filename: null as an OWN property — that path DOES NOT fire. The vulnerable shape is when the caller passes their own options object (commonly {signal: ac.signal} for abort support, {name: ...} for task labelling, etc.). These caller-built options objects inherit from Object.prototype unless the caller explicitly uses Object.create(null). Impact Two preconditions: 1. Upstream PP-source somewhere in the…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-x9g3-xrwr-cwfg

  2. Revision 1 · created ·

    Published from osv record GHSA-x9g3-xrwr-cwfg

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-55388

Advisory: piscina: Prototype Pollution Gadget → RCE via inherited options.filename
IDs: CVE-2026-55388, GHSA-x9g3-xrwr-cwfg
Record: https://patchnext.com/advisories/cve-2026-55388 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: piscina 6.0.0-rc.2, 5.2.0, 4.9.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm piscina: affected >= 5.0.0-alpha.0, <= 5.1.4; <= 4.9.2; >= 6.0.0-rc.1, < 6.0.0-rc.2; fixed in 5.2.0, 6.0.0-rc.2, 4.9.3

## Suggested inspection (read-only)
- `npm ls piscina --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on piscina.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-x9g3-xrwr-cwfg (OSV record GHSA-x9g3-xrwr-cwfg lists affected ranges: npm piscina >=5.0.0-alpha.0 =0 =6.0.0-rc.1 <6.0.0-rc.2 (fixed))
- Verified: https://github.com/advisories/GHSA-x9g3-xrwr-cwfg (GitHub-reviewed advisory GHSA-x9g3-xrwr-cwfg lists affected ranges: npm piscina >=5.0.0-alpha.0 =0 =6.0.0-rc.1 <6.0.0-rc.2)

Commands are suggestions: review each one before running it.

Loading voting…