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Rtu500 FirmwareOperating system · Hitachienergy

CVE-2021-35533

HIGH · 7.5 CVSS v3.1 Published 2021-11-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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).

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Improper input validation in the APDU parser of the Bidirectional Communication Interface (BCI) IEC 60870-5-104 function in Hitachi Energy RTU500 series CMU firmware allows remote attackers to cause device reboot via specially crafted messages. The vulnerability affects firmware versions 12.0.*, 12.2.*, and 12.4.* across all RTU500 series devices where BCI is enabled.

MitigationBy default, BCI IEC 60870-5-104 is disabled; verify BCI is not configured if not needed. If BCI is required, apply vendor firmware updates when available and implement network segmentation to restrict access to IEC 60870-5-104 ports.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Rtu500 FirmwareOperating system
Affected:= 12.0= 12.2= 12.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check firmware version
    Access the RTU500 CMU management interface or use firmware version query command to identify the installed firmware version
    Affected if Firmware version begins with 12.0, 12.2, or 12.4 (for example, 12.0.1, 12.2.3, 12.4.0)
  2. Verify BCI IEC 60870-5-104 status
    Inspect the Bidirectional Communication Interface configuration in the RTU500 to determine whether IEC 60870-5-104 protocol is enabled
    Affected if BCI IEC 60870-5-104 is explicitly enabled or configured in the device
  3. Confirm network exposure
    Review network configuration to determine if IEC 60870-5-104 ports (typically TCP port 2404) are accessible from untrusted networks
    Affected if IEC 60870-5-104 service is exposed to external or untrusted network segments

The device is affected only if it runs firmware version 12.0.x, 12.2.x, or 12.4.x AND has BCI IEC 60870-5-104 enabled; if either condition is false, the device is not vulnerable to this specific flaw.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

By default, BCI IEC 60870-5-104 is disabled; verify BCI is not configured if not needed. If BCI is required, apply vendor firmware updates when available and implement network segmentation to restrict access to IEC 60870-5-104 ports.

Recommended fix Moderate confidence
  1. Verify if the BCI IEC 60870-5-104 function is enabled or configured on the affected RTU500 CMU units
  2. If the BCI IEC 60870-5-104 function is not required for operations, disable or do not configure it to prevent exploitation
  3. If the BCI IEC 60870-5-104 function is required, consult Hitachi Energy directly for firmware updates or patches addressing this vulnerability
  4. Implement network segmentation and access controls to limit exposure of the IEC 60870-5-104 protocol to trusted sources only

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Rtu500 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-35533 in production — separate from our analysis above.

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