CVE-2026-55388

HIGHPre-NVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 79% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.1Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.1
EG Score
8.1(medium)
EPSS
21.4%
KEV
Not listed

Published

June 18, 2026

Last Modified

June 23, 2026

Advisory Details (1)

Auto-updated Jun 22, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Prototype Pollution Gadget → RCE via inherited options.filename · Advisory · piscinajs/piscina · GitHub

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

Vendor Advisories for CVE-2026-55388(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
piscina—6.0.0-rc.2—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 23× in last 7d / 54× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 23:12 UTCEG score recompute
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 10:01 UTCEG score recompute
  5. 2026-07-06 02:23 UTCEPSS rescore
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  7. 2026-07-05 20:25 UTCEG score recompute
  8. 2026-07-05 07:14 UTCEG score recompute
  9. 2026-07-05 02:31 UTCEPSS rescore
  10. 2026-07-05 02:30 UTCEPSS rescore
  11. 2026-07-04 17:52 UTCEG score recompute
  12. 2026-07-04 06:31 UTCEPSS rescore
  13. 2026-07-04 06:31 UTCEPSS rescore
  14. 2026-07-04 04:38 UTCEG score recompute
  15. 2026-07-03 15:01 UTCEG score recompute
  16. 2026-07-03 01:49 UTCEG score recompute
  17. 2026-07-02 12:39 UTCEG score recompute
  18. 2026-07-01 23:28 UTCEG score recompute
  19. 2026-07-01 15:07 UTCEPSS rescore
  20. 2026-07-01 10:17 UTCEG score recompute
  21. 2026-06-30 23:22 UTCEPSS rescore
  22. 2026-06-30 21:06 UTCEG score recompute
  23. 2026-06-30 07:50 UTCEG score recompute
  24. 2026-06-29 18:38 UTCEG score recompute
  25. 2026-06-29 14:06 UTCEPSS rescore
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  1. 2026-06-29 14:06 UTCEPSS rescore
  2. 2026-06-29 05:27 UTCEG score recompute
  3. 2026-06-28 16:10 UTCEG score recompute
  4. 2026-06-28 14:07 UTCEPSS rescore
  5. 2026-06-28 04:56 UTCEPSS rescore
  6. 2026-06-28 04:56 UTCEPSS rescore
  7. 2026-06-28 02:59 UTCEG score recompute
  8. 2026-06-27 13:48 UTCEG score recompute
  9. 2026-06-27 03:08 UTCEPSS rescore
  10. 2026-06-27 00:37 UTCEG score recompute
  11. 2026-06-26 11:26 UTCEG score recompute
  12. 2026-06-25 16:59 UTCEG score recompute
  13. 2026-06-25 13:49 UTCEPSS rescore
  14. 2026-06-25 03:47 UTCEG score recompute
  15. 2026-06-24 14:36 UTCEG score recompute
  16. 2026-06-24 14:05 UTCEPSS rescore
  17. 2026-06-24 01:25 UTCEG score recompute
  18. 2026-06-23 21:33 UTCEPSS rescore
  19. 2026-06-23 21:33 UTCEPSS rescore
  20. 2026-06-23 12:12 UTCEG score recompute
  21. 2026-06-22 23:00 UTCEG score recompute
  22. 2026-06-22 09:48 UTCEG score recompute
  23. 2026-06-21 20:35 UTCEG score recompute
  24. 2026-06-21 07:22 UTCEG score recompute
  25. 2026-06-20 18:05 UTCEG score recompute
  26. 2026-06-20 04:53 UTCEG score recompute
  27. 2026-06-19 15:31 UTCEG score recompute
  28. 2026-06-19 02:20 UTCEG score recompute
  29. 2026-06-18 13:07 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55388?
CVE-2026-55388 is a high vulnerability published on June 18, 2026. 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…
When was CVE-2026-55388 disclosed?
CVE-2026-55388 was first published in the National Vulnerability Database on June 18, 2026, with the most recent update on June 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55388 actively exploited?
CVE-2026-55388 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55388?
CVE-2026-55388 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-55388?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55388, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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