What is CVE-2026-8066?

CVE-2026-8066 is a critical-severity vulnerability in Hitachi Energy Rtu500 Series Cmu Firmware, classified under Relative Path Traversal. CVSS score: 9.1/10. Published 2026-09-29.

How severe is CVE-2026-8066?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Path Traversal in Hitachi Energy Rtu500 Series Cmu Firmware

CVE-2026-8066

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.

Published 2026-09-29 · last modified 2026-09-29.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Hitachi Energy Rtu500 Series Cmu Firmware

Weakness classification (CWE)

CWE-23 — Relative Path Traversal

References

publisher.hitachienergy.com/preview

Frequently asked questions

What is CVE-2026-8066?: CVE-2026-8066 is a critical-severity vulnerability in Hitachi Energy Rtu500 Series Cmu Firmware, classified under Relative Path Traversal. CVSS score: 9.1/10. Published 2026-09-29.
How severe is CVE-2026-8066?: Critical severity. CVSS v3 base score is 9.1 out of 10.