CVE-2026-8066

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreHIGH confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-09-29. A secondary CVSS source baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
9.1EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.7%CVSS: 9.1Exploit: None knownExposed services: Not assessed

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

A directory traversal vulnerability in the file upload functionality of Hitachi Energy RTU500 end-of-life versions allows an unauthenticated attacker to write or overwrite arbitrary files on the device file system. Depending on the files affected, successful exploitation could result in unauthorized modification of device data or disruption of the device’s intended operation.

CVSS v3
9.1
EG Score
9.1CRITICALhigh confidence
EG Risk
56
EG Risk 56/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.7%
EPSS %ILE
52nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 29, 2026

Last Modified

September 29, 2026

Advisory Details (1)

Auto-updated Sep 29, 2026
No patch confirmed yet.
generic

Hitachi Energy Publisher

https://publisher.hitachienergy.com/preview?DocumentID=8DBD000251&LanguageCode=en&DocumentPartId=&Action=Launch

Vendor Advisories for CVE-2026-8066(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 52× in last 7d / 52× 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. 2026-10-05 10:59 UTCGHSA enrichment
  2. 2026-10-05 06:52 UTCGHSA enrichment
  3. 2026-10-05 02:44 UTCEG score recompute
  4. 2026-10-05 02:44 UTCGHSA enrichment
  5. 2026-10-04 23:22 UTCEPSS rescore
  6. 2026-10-04 22:36 UTCGHSA enrichment
  7. 2026-10-04 18:27 UTCGHSA enrichment
  8. 2026-10-04 14:14 UTCGHSA enrichment
  9. 2026-10-04 10:04 UTCGHSA enrichment
  10. 2026-10-04 05:55 UTCGHSA enrichment
  11. 2026-10-04 01:47 UTCGHSA enrichment
  12. 2026-10-03 21:39 UTCGHSA enrichment
  13. 2026-10-03 17:30 UTCEG score recompute
  14. 2026-10-03 17:30 UTCGHSA enrichment
  15. 2026-10-03 13:23 UTCGHSA enrichment
  16. 2026-10-03 09:14 UTCGHSA enrichment
  17. 2026-10-03 05:05 UTCGHSA enrichment
  18. 2026-10-03 00:57 UTCGHSA enrichment
  19. 2026-10-02 20:49 UTCEG score recompute
  20. 2026-10-02 20:49 UTCGHSA enrichment
  21. 2026-10-02 16:41 UTCGHSA enrichment
  22. 2026-10-02 12:29 UTCGHSA enrichment
  23. 2026-10-02 08:21 UTCGHSA enrichment
  24. 2026-10-02 04:13 UTCGHSA enrichment
  25. 2026-10-02 00:02 UTCEG score recompute
Show 27 more
  1. 2026-10-02 00:02 UTCGHSA enrichment
  2. 2026-10-01 19:51 UTCEPSS rescore
  3. 2026-10-01 19:43 UTCGHSA enrichment
  4. 2026-10-01 15:35 UTCGHSA enrichment
  5. 2026-10-01 11:27 UTCGHSA enrichment
  6. 2026-10-01 07:18 UTCGHSA enrichment
  7. 2026-10-01 03:10 UTCGHSA enrichment
  8. 2026-09-30 23:02 UTCGHSA enrichment
  9. 2026-09-30 18:53 UTCEG score recompute
  10. 2026-09-30 18:53 UTCGHSA enrichment
  11. 2026-09-30 15:04 UTCEPSS rescore
  12. 2026-09-30 14:45 UTCGHSA enrichment
  13. 2026-09-30 10:37 UTCGHSA enrichment
  14. 2026-09-30 06:27 UTCGHSA enrichment
  15. 2026-09-30 02:18 UTCGHSA enrichment
  16. 2026-09-29 22:10 UTCGHSA enrichment
  17. 2026-09-29 16:41 UTCEG score recompute
  18. 2026-09-29 16:40 UTCGHSA enrichment
  19. 2026-09-29 15:58 UTCEG score recompute
  20. 2026-09-29 15:58 UTCGHSA enrichment
  21. 2026-09-29 13:43 UTCEG score recompute
  22. 2026-09-29 13:43 UTCGHSA enrichment
  23. 2026-09-29 13:11 UTCEG score recompute
  24. 2026-09-29 13:11 UTCGHSA enrichment
  25. 2026-09-29 10:42 UTCEG score recompute
  26. 2026-09-29 09:29 UTCEG score recompute
  27. 2026-09-29 09:28 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-8066?
CVE-2026-8066 is a critical vulnerability published on September 29, 2026. A directory traversal vulnerability in the file upload functionality of Hitachi Energy RTU500 end-of-life versions allows an unauthenticated attacker to write or overwrite arbitrary files on the device file system. Depending on the files affected, successful exploitation could result in…
When was CVE-2026-8066 disclosed?
CVE-2026-8066 was first published on September 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8066 actively exploited?
CVE-2026-8066 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.7% probability of exploitation in the next 30 days (52nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-8066?
CVE-2026-8066 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-8066?
No fix for CVE-2026-8066 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-8066 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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