CVE-2026-1773

High

Published: 24 February 2026

Published

24 February 2026

Modified

26 May 2026

KEV Added

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Patch

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CVSS Score v4 8.7 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

EPSS Score 0.0041 32.7th percentile

Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-1773 is a high-severity Incomplete List of Disallowed Inputs (CWE-184) vulnerability in Hitachienergy Rtu540 Firmware. Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 32.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SI-10 (Information Input Validation).

Deeper analysis

CVE-2026-1773 is a vulnerability in the IEC 60870-5-104 protocol that can cause a denial of service upon reception of an invalid U-format frame. It affects Hitachi Energy products only if IEC 60870-5-104 bi-directional functionality is configured. The issue is rated with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is associated with CWE-184.

A remote network-based attacker requires no privileges or user interaction to exploit this vulnerability by sending an invalid U-format frame, potentially disrupting service availability on affected products.

The Hitachi Energy advisory (https://publisher.hitachienergy.com/preview?DocumentID=8DBD000237&LanguageCode=en&DocumentPartId=&Action=Launch) notes that enabling secure communication following IEC 62351-3 does not remediate the vulnerability but mitigates the risk of exploitation.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-8462

Vulnerability details

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.

CWE(s): CWE-184

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1499.004 Application or System Exploitation Impact

Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.

attack.mitre.org →

Why these techniques?

Remote unauthenticated network exploit of protocol implementation flaw directly enables T1190 (public-facing application) and T1499.004 (application exploitation for endpoint DoS).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0