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R08sfcpu FirmwareOperating system · Mitsubishielectric

CVE-2021-20599

HIGH · 7.5 CVSS v3.1 Published 2021-10-14
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
Cleartext Transmission of Sensitive InformationCleartext transmission of sensitive information vulnerability in MELSEC iQ-R series Safety CPU R08/16/32/120SFCPU firmware versions "26" and prior and MELSEC iQ-R series SIL2 Process CPU R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to login to a target CPU module by obtaining credentials other than password.

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 MELSEC iQ-R series Safety CPU and SIL2 Process CPU modules allows sensitive credentials to be transmitted in cleartext (unencrypted). A remote unauthenticated attacker can intercept these credentials and use them to login to the target CPU module without knowing the actual password, bypassing authentication.

MitigationUpgrade firmware to versions beyond '26' for Safety CPU and '11' for SIL2 Process CPU, and ensure all network communications to these industrial controllers use encrypted protocols such as TLS.

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 the installed CPU module model
    Locate the physical CPU module or check system configuration to confirm whether the device is an R08sfcpu, R16sfcpu, R32sfcpu, R120sfcpu (Safety CPU) or R08psfcpu, R16psfcpu, R32psfcpu, R120psfcpu (SIL2 Process CPU)
    Affected if The model matches any of the affected product names listed in the CVE (R08sfcpu, R16sfcpu, R32sfcpu, R120sfcpu, R08psfcpu, R16psfcpu, R32psfcpu, R120psfcpu)
  2. Check the firmware version
    Access the CPU module configuration via Mitsubishi programming software (such as GX Works3) or the device web interface and retrieve the firmware version information
    Affected if The firmware version is any version (all versions of these models are affected per the CVE)
  3. Inspect network protocol settings
    Review the CPU module network configuration settings in GX Works3 or the device web interface to determine whether communications are configured to use unencrypted protocols (such as HTTP, non-TLS MELSEC protocols, or open network ports used for authentication)
    Affected if The device is configured to allow or use unencrypted network protocols for user authentication or credential transmission
  4. Verify encryption is enforced for remote access
    Check whether remote access to the CPU module requires encrypted protocols such as HTTPS or TLS-encrypted connections, and confirm that fallback to cleartext protocols is disabled
    Affected if Remote access or authentication can occur over unencrypted channels without TLS protection

You are affected if you have any of the listed Safety CPU or SIL2 Process CPU models (R08/16/32/120sfcpu or R08/16/32/120psfcpu) and your network configuration allows authentication or credential transmission over unencrypted protocols.

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

Upgrade firmware to versions beyond '26' for Safety CPU and '11' for SIL2 Process CPU, and ensure all network communications to these industrial controllers use encrypted protocols such as TLS.

Fix this in R08sfcpu Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2021-20599 in production — separate from our analysis above.

No notes yet

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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