CVE-2026-1773

High

Published: 24 February 2026

Published

24 February 2026

Modified

27 February 2026

KEV Added

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Patch

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CVSS Score 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Score 0.0003 7.6th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

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 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 7.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique.

Threat & Defense Details

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-8 Spam Protection

addresses: CWE-184

Spam filters rely on evolving blacklists, signatures, and heuristics of disallowed message patterns; keeping them updated per the control directly mitigates incomplete disallowed-input lists.

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 v18.1

NVD Description

IEC 60870-5-104: 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.

Deeper analysisAI

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.