Vulnerability · Published Sep 29, 2026 · Assigned by Hitachi Energy
CVE-2026-8066
Critical 9.1
In plain English
A critical-severity security flaw in RTU500 series CMU firmware from Hitachi Energy. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 55% of all known vulnerabilities).
Official description
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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Hitachi Energy | RTU500 series CMU firmware | 9.0 – before 12.0 |
Weakness: CWE-23 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H