RCE in Piscinajs Piscina

CVE-2026-55388

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.

Vulnerability class: RCE (Remote Code Execution)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (37.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-55388: held from 0.005 to 0.005.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

  • Piscinajs Piscina — versions < 4.9.3, >= 5.0.0-alpha.0, < 5.2.0, >= 6.0.0-rc.1, < 6.0.0-rc.2

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55388?
CVE-2026-55388 is a high-severity vulnerability in Piscinajs Piscina, classified under Code Injection. CVSS score: 8.1/10. Published 2026-06-22.
How severe is CVE-2026-55388?
High severity. CVSS v3 base score is 8.1 out of 10.