CVE-2021-35533: Hitachienergy RTU500 Firmware

High severity, CVSS 7.5. EPSS: 1% chance of exploitation in the next 30 days.

Improper Input Validation vulnerability in the APDU parser in the Bidirectional Communication Interface (BCI) IEC 60870-5-104 function of Hitachi Energy RTU500 series allows an attacker to cause the receiving RTU500 CMU of which the BCI is enabled to reboot when receiving a specially crafted message. By default, BCI IEC 60870-5-104 function is disabled (not configured). This issue affects: Hitachi Energy RTU500 series CMU Firmware version 12.0.* (all versions); CMU Firmware version 12.2.* (all versions); CMU Firmware version 12.4.* (all versions).

Affected products

• Hitachienergy RTU500 Firmware: version 12.0 only; version 12.2 only; version 12.4 only

Published 2021-11-26. Last modified 2026-06-17.