Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:N) | No confidentiality impact |
| Integrity (VI:N) | No integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
About Hitachienergy Rtu540 Firmware
CVE-2026-1773 affects Hitachienergy Rtu540 Firmware, a product from Hitachienergy. Before acting, confirm where Hitachienergy Rtu540 Firmware runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: IEC 60870-5-104 used in RTU500: Potential Denial of Service impact on reception of invalid U-format frame. Product is only affected if IEC 60870-5-104 bi-directional functionality is configured. Enabling secure communication following IEC 62351-3 does not remediate the vulnerability but mitigates the risk of exploitation.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Hitachienergy Rtu540 Firmware |
| Affected versions | Rtu540 Firmware from 12.7.1 up to and including 12.7.7; Rtu540 Firmware from 13.5.1 up to and including 13.5.4; Rtu540 Firmware from 13.6.1 up to and including 13.6.2; Rtu540 Firmware from 13.7.1 before 13.7.8; Rtu540 Firmware 13.8.1; Rtu560 Firmware from 12.7.1 up to and including 12.7.7; Rtu560 Firmware from 13.5.1 up to and including 13.5.4; Rtu560 Firmware from 13.6.1 up to and including 13.6.2; Rtu560 Firmware from 13.7.1 before 13.7.8; Rtu560 Firmware 13.8.1; Rtu520 Firmware from 12.7.1 up to and including 12.7.7; Rtu520 Firmware from 13.5.1 up to and including 13.5.4 |
| Published | Feb 24, 2026 |
| Last modified | Jun 17, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | cybersecurity@hitachienergy.com |
How to detect it
- Inventory every instance of Hitachienergy Rtu540 Firmware and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Hitachienergy Rtu540 Firmware named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Hitachienergy Rtu540 Firmware to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
Technical References
Frequently asked questions
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