piscina: Prototype-pollution gadget in ThreadPool.options allows RCE via execArgv / loadBalancer / env

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.2 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-102992: 0.51% estimated exploitation activity in the next 30 days; percentile 43.73 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A prototype-pollution gadget in ThreadPool.options allows an attacker who can pollute Object.prototype to execute arbitrary code in Piscina worker threads, invoke arbitrary functions during task scheduling, or inject environment variables into workers. The root cause is that ThreadPool.options is created as a plain object inheriting from Object.prototype, so any option without an explicit default in kDefaultOptions can be supplied via the prototype chain. Details In src/index.ts the ThreadPool constructor builds the resolved options object as a plain object: Because this object has Object.prototype as its prototype, reads for properties that are not own properties of the object and are not present in kDefaultOptions fall back to Object.prototype. This means a prototype-pollution primitive (e.g. from a vulnerable merge() or JSON.parse merge elsewhere in the application) can inject values for execArgv, env, loadBalancer, argv, workerData, resourceLimits, niceIncrement,…

Published by the source

1 Oct 2026, 15:03 UTC

Last modified by the source

1 Oct 2026, 15:15 UTC

Source last checked

26 Oct 2026, 13:06 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-67c8-pqhq-4rmx

2. Revision 3 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-67c8-pqhq-4rmx

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-67c8-pqhq-4rmx

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# Patch Next advisory brief: CVE-2026-102992

Advisory: piscina: Prototype-pollution gadget in ThreadPool.options allows RCE via execArgv / loadBalancer / env
IDs: CVE-2026-102992, GHSA-67c8-pqhq-4rmx
Record: https://patchnext.com/advisories/cve-2026-102992 (revision 4, source checked 26 Oct 2026, 13:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.2)
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.5, 5.3.2, 4.9.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm piscina: affected >= 5.0.0, < 5.3.2; < 4.9.4; >= 6.0.0-rc.1, < 6.0.0-rc.5; fixed in 6.0.0-rc.5, 5.3.2, 4.9.4

## 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://github.com/advisories/GHSA-67c8-pqhq-4rmx (GitHub-reviewed advisory GHSA-67c8-pqhq-4rmx lists affected ranges: npm piscina >=5.0.0 =0 =6.0.0-rc.1 <6.0.0-rc.5)
- Verified: https://osv.dev/vulnerability/GHSA-67c8-pqhq-4rmx (OSV record GHSA-67c8-pqhq-4rmx lists affected ranges: npm piscina >=5.0.0 =0 =6.0.0-rc.1 <6.0.0-rc.5 (fixed))

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