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R08sfcpu FirmwareOperating system · Mitsubishielectric

CVE-2021-20594

HIGH · 7.5 CVSS v3.1 Published 2021-08-06
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
Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Mitsubishi Electric MELSEC iQ-R series Safety CPU modules R08/16/32/120SFCPU firmware versions "26" and prior and Mitsubishi Electric MELSEC iQ-R series SIL2 Process CPU modules R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to acquire legitimate user names registered in the module via brute-force attack on user names.

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

This vulnerability in Mitsubishi Electric MELSEC iQ-R series Safety and SIL2 Process CPU modules allows remote unauthenticated attackers to enumerate valid user names registered in the module through brute-force attack. The system exposes whether a username exists via its authentication responses, enabling attackers to identify valid accounts before mounting password attacks.

MitigationUpdate firmware to version 27 or later for Safety CPU modules (R08/16/32/120SFCPU) and version 12 or later for SIL2 Process CPU modules (R08/16/32/120PSFCPU). Additionally, implement network segmentation and account lockout policies to limit exposure.

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
R08sfcpu FirmwareOperating system
Affected:all versions
R16sfcpu FirmwareOperating system
Affected:all versions
R32sfcpu FirmwareOperating system
Affected:all versions
R120sfcpu FirmwareOperating system
Affected:all versions
R08psfcpu FirmwareOperating system
Affected:all versions
R16psfcpu FirmwareOperating system
Affected:all versions
R32psfcpu FirmwareOperating system
Affected:all versions
R120psfcpu FirmwareOperating system
Affected:all versions

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
High
Integrity
None
Availability
None

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

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. Identify MELSEC iQ-R Safety CPU modules in environment
    Review asset inventory or use network discovery to locate R08SFCPU, R16SFCPU, R32SFCPU, or R120SFCPU modules. These are Safety CPU modules in the MELSEC iQ-R series.
    Affected if Any of these four model numbers (R08/16/32/120SFCPU) are present on the network, regardless of firmware version, since all versions are affected.
  2. Identify MELSEC iQ-R SIL2 Process CPU modules in environment
    Review asset inventory or use network discovery to locate R08PSFCPU, R16PSFCPU, R32PSFCPU, or R120PSFCPU modules. These are SIL2 Process CPU modules in the MELSEC iQ-R series.
    Affected if Any of these four model numbers (R08/16/32/120PSFCPU) are present on the network, regardless of firmware version, since all versions are affected.
  3. Check Safety CPU firmware version
    Access the CPU module via engineering software (such as GX Works3) or the module's web interface. Navigate to the module information or system information section to retrieve the firmware version. For Safety CPU modules (RxxSFCPU), the affected versions are all versions prior to version 27.
    Affected if The firmware version is any version before 27, or if the version cannot be determined but the module is a Safety CPU model (R08/16/32/120SFCPU).
  4. Check SIL2 Process CPU firmware version
    Access the CPU module via engineering software (such as GX Works3) or the module's web interface. Navigate to the module information or system information section to retrieve the firmware version. For SIL2 Process CPU modules (RxxPSFCPU), the affected versions are all versions prior to version 12.
    Affected if The firmware version is any version before 12, or if the version cannot be determined but the module is a SIL2 Process CPU model (R08/16/32/120PSFCPU).

You are affected if any MELSEC iQ-R series Safety CPU (R08/16/32/120SFCPU) or SIL2 Process CPU (R08/16/32/120PSFCPU) modules are present in your environment with firmware versions below 27 (Safety CPU) or below 12 (SIL2 Process CPU), since all versions of these models are vulnerable to user enumeration.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update firmware to version 27 or later for Safety CPU modules (R08/16/32/120SFCPU) and version 12 or later for SIL2 Process CPU modules (R08/16/32/120PSFCPU). Additionally, implement network segmentation and account lockout policies to limit exposure.

Fix this in R08sfcpu Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,180
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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-2021-20594 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data