Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M

CVE-2026-55388piscina: Prototype Pollution Gadget → RCE via inherited options.filename

High 8.1

In plain English

A high-severity code injection in piscina from piscinajs. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High

Exploit odds (30 days)0.5%top 58.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	piscina	5.2.0	GHSA-x9g3-xrwr-cwfg
npm	piscina	4.9.3	GHSA-x9g3-xrwr-cwfg
npm	piscina	6.0.0-rc.2	GHSA-x9g3-xrwr-cwfg

Affected products (as reported)

Vendor	Product	Versions
piscinajs	piscina	< 4.9.3>= 5.0.0-alpha.0, < 5.2.0>= 6.0.0-rc.1, < 6.0.0-rc.2

Weakness: CWE-94, CWE-1321 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg x_refsource_CONFIRM