CVE-2021-35533Network attack vector

Remote reboot via crafted IEC 60870-5-104 APDU

Published Nov 26, 2021 · Updated Sep 16, 2024

Improper input validation in the RTU500 Series APDU parser allows remote attackers to reboot affected CMUs with a crafted IEC 60870-5-104 message. The parser processes the crafted APDU without adequate validation, causing the receiving CMU to restart. Affected CMU Firmware branches are 12.0., 12.2., and 12.4.*; BCI is disabled by default, and exploitation interrupts service by rebooting the CMU.

CVSS severity7.5
High
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in the RTU500 Series APDU parser allows remote attackers to reboot affected CMUs with a crafted IEC 60870-5-104 message. The parser processes the crafted APDU without adequate validation, causing the receiving CMU to restart. Affected CMU Firmware branches are 12.0., 12.2., and 12.4.*; BCI is disabled by default, and exploitation interrupts service by rebooting the CMU.

The record

CVE
CVE-2021-35533
Published
Nov 26, 2021
Updated
Sep 16, 2024
Vendor
Hitachi Energy
Product
RTU500 Series
Classifications
CWE-20, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=CMU Firmware version 12.0 <=12.0.*
  2. Affected versionversion=CMU Firmware version 12.2 <=12.2.*
  3. Affected versionversion=CMU Firmware version 12.4 <=12.4.*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hitachi Energy · RTU500 Seriesversion=CMU Firmware version 12.0 <=12.0.*; version=CMU Firmware version 12.2 <=12.2.*; version=CMU Firmware version 12.4 <=12.4.*

Published CVSS scores

7.1NISTAV:N/AC:M/Au:N/C:N/I:N/A:C
7.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T0814Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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