CVE-2026-8066 Path traversal in RTU500 series CMU firmware
Unauthenticated attackers can exploit a directory traversal flaw in Hitachi RTU500 firmware to write arbitrary files, potentially modifying data or disrupting operations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-8066?
CVE-2026-8066 is a critical path traversal vulnerability in Hitachi Energy RTU500 series CMU firmware, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-23
Which versions are affected by CVE-2026-8066?
How do I fix CVE-2026-8066?
No fix has been published for CVE-2026-8066 yet. Limit exposure of the affected software until one is available.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-8066 being exploited?
There is no known exploitation of CVE-2026-8066 in the wild and no public exploit code.
Sources
Also known as GHSA-27cq-c5r3-854p.