CVE-2026-8066: Hitachi Energy RTU500 Series Cmu Firmware

Critical severity, CVSS 9.1. EPSS: 0.7% chance of exploitation in the next 30 days.

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.

Affected products

• Hitachi Energy RTU500 Series Cmu Firmware: from 9.0, before 12.0 (fixed in 12.0)

Published 2026-09-29. Last modified 2026-09-29.