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

published 2026-06-18 4 mo ago modified 2026-11-03 5 d ago also GHSA-x9g3-xrwr-cwfg , EUVD-2026-38320

cvss: 8.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

npm piscina 4.9.3, 5.2.0, 6.0.0-rc.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-55388 updated 2026-06-28 cvss 8.1

piscina: piscina: Arbitrary code execution via prototype pollution of filename option

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 4 mo ago (2026-06-23)

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub	3.1	8.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
npm	piscina	>=5.0.0-alpha.0, <5.2.0 <4.9.3 >=6.0.0-rc.1, <6.0.0-rc.2	5.2.0 4.9.3 6.0.0-rc.2

Affected products

piscinajs piscina

Classification

Weakness

CWE-94 Improper Control of Generation of Code
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

github.com /piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg
exploit, web
github.com /piscinajs/piscina
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary