Tinypool: Prototype Pollution gadget in worker options leads to Remote Code Execution

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-104848: 0.50% estimated exploitation activity in the next 30 days; percentile 42.70 (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.

tinypool passes worker options to new Worker() by reading them off a plain object whose prototype is Object.prototype. Options the application did not set are resolved through the prototype chain and then passed explicitly to workerthreads.Worker. Node core ignores Worker options inherited from Object.prototype. By reading them and passing them explicitly, tinypool re-materialises them as own properties and defeats that protection. Two keys reach code execution: 1. execArgv — polluting Object.prototype.execArgv = ['--require', '/path/to/attacker.js'] causes every pool worker to load the attacker's script. 2. env — polluting Object.prototype.env = { NODEOPTIONS: '--require /path/to/attacker.js' } achieves the same via environment injection. Root cause dist/index.js lines 508-511: this.options is built at line 470 via object spread: Impact Arbitrary code execution inside every worker the pool spawns, with the privileges of the host process. Because tinypool is the worker pool behind…

Published by the source

5 Oct 2026, 22:50 UTC

Last modified by the source

5 Oct 2026, 23:00 UTC

Source last checked

26 Oct 2026, 13:06 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5gmw-xhrv-c9v3

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-5gmw-xhrv-c9v3

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-5gmw-xhrv-c9v3

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# Patch Next advisory brief: CVE-2026-104848

Advisory: Tinypool: Prototype Pollution gadget in worker options leads to Remote Code Execution
IDs: CVE-2026-104848, GHSA-5gmw-xhrv-c9v3
Record: https://patchnext.com/advisories/cve-2026-104848 (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 9.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tinypool 2.1.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm tinypool: affected <= 2.1.0; fixed in 2.1.1

## Suggested inspection (read-only)
- `npm ls tinypool --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 tinypool.
- 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-5gmw-xhrv-c9v3 (GitHub-reviewed advisory GHSA-5gmw-xhrv-c9v3 lists affected ranges: npm tinypool >=0 <=2.1.0)
- Verified: https://osv.dev/vulnerability/GHSA-5gmw-xhrv-c9v3 (OSV record GHSA-5gmw-xhrv-c9v3 lists affected ranges: npm tinypool >=0 <2.1.1 (fixed))

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