TI-2026-39959 Aliases CVE-2026-55388 GHSA-x9g3-xrwr-cwfg

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

HIGH 70CWE-1321Published 2026-06-22 · Updated 2026-11-03

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-94.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00483 41st percentileScored 2026-11-07

Fix Fixed piscina (piscinajs): 4.9.3, 5.2.0, 6.0.0-rc.2piscina (npm): 5.2.0, 4.9.3, 6.0.0-rc.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
piscinajs	piscina	before 4.9.3; 5.0.0-alpha.0 to before 5.2.0; 6.0.0-rc.1 to before 6.0.0-rc.2	4.9.3, 5.2.0, 6.0.0-rc.2	Patch available	CNA
—	piscina (npm)	5.0.0-alpha.0 to before 5.2.0	5.2.0	Patch available	GHSA-x9g3-xrwr-cwfg
—	piscina (npm)	before 4.9.3	4.9.3	Patch available	GHSA-x9g3-xrwr-cwfg
—	piscina (npm)	6.0.0-rc.1 to before 6.0.0-rc.2	6.0.0-rc.2	Patch available	GHSA-x9g3-xrwr-cwfg

piscina Vendorpiscinajs Affected before 4.9.3; 5.0.0-alpha.0 to before 5.2.0; 6.0.0-rc.1 to before 6.0.0-rc.2 Fixed in 4.9.3, 5.2.0, 6.0.0-rc.2 Patch available CNA
piscina (npm) Vendor— Affected 5.0.0-alpha.0 to before 5.2.0 Fixed in 5.2.0 Patch available GHSA-x9g3-xrwr-cwfg
piscina (npm) Vendor— Affected before 4.9.3 Fixed in 4.9.3 Patch available GHSA-x9g3-xrwr-cwfg
piscina (npm) Vendor— Affected 6.0.0-rc.1 to before 6.0.0-rc.2 Fixed in 6.0.0-rc.2 Patch available GHSA-x9g3-xrwr-cwfg

Remediation

Fix · CNA piscina (piscinajs) Fixed in 4.9.3, 5.2.0, 6.0.0-rc.2
Fix · GHSA-x9g3-xrwr-cwfg piscina (npm) Fixed in 5.2.0 Advisory →
Fix · GHSA-x9g3-xrwr-cwfg piscina (npm) Fixed in 4.9.3 Advisory →
Fix · GHSA-x9g3-xrwr-cwfg piscina (npm) Fixed in 6.0.0-rc.2 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product

Red Hat

Timeline

2026-10-02 Threatist record created from CVE-2026-55388
2026-10-03 Alias added: GHSA-x9g3-xrwr-cwfg

References

Other 2

TI-2026-65549 piscina: Prototype-pollution gadget in ThreadPool.options allows RCE via execArgv / loadBalancer / env CVSS 4.0CRITICAL 9.2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences