CVE-2021-35533

highpriority · track · 30EPSS 0.009 · 61 %ileEUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

0.95% (61st) EPSS

CVSS 7.1 · high

Is it mine?

12 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · cisa_csaf_ot · nvd

EPSS · scored 2026-10-27

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).

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

No vendor fix yet; a mitigation is available.

MitigationRTU500 series CMU Firmware Version 12.0cisa_csaf_ot
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.
MitigationRTU500 series CMU Firmware Version 12.2cisa_csaf_ot
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.
MitigationRTU500 series CMU Firmware Version 12.4cisa_csaf_ot
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.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5

v2.07.1highAV:N/AC:M/Au:N/C:N/I:N/A:Cprimary · NVD / NIST USexploitability 8.6 · impact 6.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.07.5highCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · CISA US

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · ENISA EU

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · cybersecurity@hitachienergy.comexploitability 3.9 · impact 3.6

v3.16.9mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-20USprimaryCWE-20US

affected products (12)

Products and version ranges known to be affected.

RTU500 series CMU Firmware Version 12.0: All versionsall versionscisa_csaf_otUS
RTU500 series CMU Firmware Version 12.2: All versionsall versionscisa_csaf_otUS
RTU500 series CMU Firmware Version 12.4: All versionsall versionscisa_csaf_otUS
Hitachi Energy RTU500 series CMU Firmware Version 12.0all versionscisa_csaf_otUS
Hitachi Energy RTU500 series CMU Firmware Version 12.2all versionscisa_csaf_otUS
Hitachi Energy RTU500 series CMU Firmware Version 12.4all versionscisa_csaf_otUS
Hitachi Energy RTU500 series≤ CMU Firmware version 12.2 ≤12.2.*enisa_euvdEU
Hitachi Energy RTU500 series≤ CMU Firmware version 12.0 ≤12.0.*enisa_euvdEU
Hitachi Energy RTU500 series≤ CMU Firmware version 12.4 ≤12.4.*enisa_euvdEU
hitachienergy rtu500 firmware= 12.0nvdUScpe:2.3:o:hitachienergy:rtu500_firmware:*:*:*:*:*:*:*:*
hitachienergy rtu500 firmware= 12.2nvdUScpe:2.3:o:hitachienergy:rtu500_firmware:*:*:*:*:*:*:*:*
hitachienergy rtu500 firmware= 12.4nvdUScpe:2.3:o:hitachienergy:rtu500_firmware:*:*:*:*:*:*:*:*

advisories (1)

Vendor and ecosystem advisories describing this.

ICSA-21-336-04Hitachi Energy RTU500 series BCI2021-12-02icsa · cisa_csaf_otUS
Successful exploitation of this vulnerability could allow a remote attacker to reboot the device.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd cisa_csaf_ot nvd NVD CVE.org MITRE

published 2021-11-26modified 2026-06-17

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references (7)

External citations — patches, advisories, analysis.

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