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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-336-04) Hitachi Energy RTU500 series BCI
3 December 2021
AusCERT Security Bulletin Summary
Product: Hitachi Energy RTU500 series BCI
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2021-35533
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ICS Advisory (ICSA-21-336-04)
Hitachi Energy RTU500 series BCI
Original release date: December 02, 2021
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1. EXECUTIVE SUMMARY
o CVSS v3 7.5
o ATTENTION: Exploitable remotely/low attack complexity
o Vendor: Hitachi Energy
o Equipment: RTU500 series Bidirectional Communication Interface (BCI)
o Vulnerability: Improper Input Validation
2. RISK EVALUATION
Successful exploitation of this vulnerability could allow a remote attacker to
reboot the device.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following firmware versions of RTU500 series, a remote terminal unit, are
o RTU500 series CMU Firmware Version 12.0: All versions
o RTU500 series CMU Firmware Version 12.2: All versions
o RTU500 series CMU Firmware Version 12.4: All versions
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER INPUT VALIDATION CWE-20
An issue exists in the BCI IEC 60870-5-104 function included in the affected
products. If BCI IEC 60870-5-104 is enabled and configured, an attacker could
exploit the vulnerability by sending a specially crafted message to the
affected product, causing it to reboot. This vulnerability is caused by the
validation error in the APDU parser of the BCI IEC 60870-5-104 function.
CVE-2021-35533 has been assigned to this vulnerability. A CVSS v3 base score of
7.5 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS: Energy
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Switzerland
Hitachi Energy reported this vulnerability to CISA.
Hitachi Energy recommends the following:
o Disable BCI IEC 60870-5-104 function by configuration if it is not used.
Note: By default, the BCI IEC 60870-5-104 is disabled.
o Update to RTU500 series CMU Firmware Version 188.8.131.52 or later (e.g.,
RTU500 CMU Firmware Version 12.7.* or CMU Firmware Version 13.2.* or
Please see Hitachi Energy advisory 8DBD000063 for additional mitigation and
Hitachi Energy recommends the following security practices and firewall
configurations to help protect process control networks from attacks that
originate from outside the network:
o Physically protect process control systems from direct access by
o Do not directly connect to the Internet.
o Separated from other networks by means of a firewall system with a minimal
number of ports exposed.
o Process control systems should not be used for Internet surfing, instant
messaging, or receiving e-mails.
o Portable computers and removable storage media should be carefully scanned
for viruses before they are connected to a control system.CISA reminds
organizations to perform proper impact analysis and risk assessment prior
to deploying defensive measures.
CISA also provides a section for control systems security recommended practices
on the ICS webpage on us-cert.cisa.gov . Several recommended practices are
available for reading and download, including Improving Industrial Control
Systems Cybersecurity with Defense-in-Depth Strategies .
Additional mitigation guidance and recommended practices are publicly available
on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to CISA for tracking
and correlation against other incidents.
No known public exploits specifically target this vulnerability.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
CISA continuously strives to improve its products and services. You can help by
choosing one of the links below to provide feedback about this product.
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