Hitachi Energy RTU500 Infinite Loop (CVE-2026-32777)

medium Tenable OT Security Plugin ID 505375

Synopsis

The remote OT asset is affected by a vulnerability.

Description

libexpat before 2.7.5 allows an infinite loop while parsing DTD content, causing Denial of Service impact.

Product is only affected if IEC 61850 functionality is configured.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.

Solution

Upgrade the RTU500 series CMU firmware to a fixed version (13.8.2, or 13.7.9 / 12.7.8 depending on the installed branch as listed in the Hitachi Energy advisory) and apply the general mitigation factors and workarounds described in the advisory.

Plugin Details

Severity: Medium

ID: 505375

File Name: tenable_ot_abb_CVE-2026-32777.nasl

Version: 1.1

Type: Remote

Family: Tenable.ot

Published: 6/17/2026

Updated: 6/17/2026

Supported Sensors: Tenable OT Security

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Vulnerability Information

CPE: cpe:/o:hitachienergy:rtu520_firmware:13.8.1, cpe:/o:hitachienergy:rtu530_firmware:13.8.1, cpe:/o:hitachienergy:rtu540_firmware:13.8.1, cpe:/o:hitachienergy:rtu560_firmware:13.8.1, cpe:/o:hitachienergy:rtu530_firmware:13.6, cpe:/o:hitachienergy:rtu530_firmware:13.7, cpe:/o:hitachienergy:rtu560_firmware:13.5, cpe:/o:hitachienergy:rtu540_firmware:13.5, cpe:/o:hitachienergy:rtu560_firmware:13.7, cpe:/o:hitachienergy:rtu520_firmware:13.7, cpe:/o:hitachienergy:rtu530_firmware:13.5, cpe:/o:hitachienergy:rtu540_firmware:13.6, cpe:/o:hitachienergy:rtu520_firmware:13.6, cpe:/o:hitachienergy:rtu520_firmware:13.5, cpe:/o:hitachienergy:rtu560_firmware:13.6, cpe:/o:hitachienergy:rtu540_firmware:13.7

Required KB Items: Tenable.ot/ABB

Patch Publication Date: 5/26/2026

Vulnerability Publication Date: 5/26/2026

Reference Information

CVE: CVE-2026-32777

CWE: 835

ICSA: 26-155-04

Detections

Analytics