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CVE Record

CVE-2021-20598: Overly Restrictive Account Lockout Mechanism vulnerability in Mitsubishi Electric MELSEC iQ-R series CPU mo...

Overly Restrictive Account Lockout Mechanism vulnerability in Mitsubishi Electric MELSEC iQ-R series CPU modules (R08/16/32/120SFCPU all versions, R08/16/32/120PSFCPU all versions) allows a remote unauthenticated attacker to lockout a legitimate user by continuously trying login with incorrect password.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This flaw can let an unauthenticated remote actor lock legitimate users out of affected Mitsubishi Electric MELSEC iQ-R safety CPU modules by repeatedly attempting logins with wrong passwords. The business risk is operational disruption and delayed maintenance or response, not evidence of code execution or data theft from the provided sources.

Executive priority

Treat this as a targeted operational availability risk for safety controller environments. Prioritize sites where affected modules are remotely reachable or support critical production and safety operations.

Technical view

CVE-2021-20598 is an account lockout weakness affecting Mitsubishi Electric MELSEC iQ-R R08/16/32/120SFCPU and R08/16/32/120PSFCPU modules, all versions. The source description says continuous incorrect login attempts can trigger lockout of legitimate users. No CVSS, CWE, patch detail, or exploit method is provided in the bundle.

Likely exposure

Exposure is most relevant where affected MELSEC iQ-R CPU module login interfaces are reachable over plant, engineering, remote-access, or improperly segmented networks. Internet exposure is not stated in the sources and should not be assumed without asset validation.

Exploitation context

The bundle does not cite active exploitation, and CISA KEV status is false. The described attack requires remote network reachability to the login function and no authentication. Impact is denial of legitimate access through lockout.

Researcher notes

The public bundle identifies affected products and the lockout behavior but lacks CVSS, CWE, detailed preconditions, patch status, and proof of exploitation. Avoid destructive validation because the vulnerability condition itself can deny access to legitimate users.

Mitigation direction

  • Review Mitsubishi Electric PSIRT 2021-010 and JVN guidance for supported mitigations or updates.
  • Restrict access to affected CPU module login services to trusted engineering hosts only.
  • Use network segmentation or remote-access controls around safety CPU management paths.
  • Monitor for bursts of failed logins and unexpected lockout events.
  • Do not assume a firmware fix from this bundle alone.

Validation and detection

  • Inventory MELSEC iQ-R R08/16/32/120SFCPU and R08/16/32/120PSFCPU modules.
  • Confirm whether management or login services are reachable from untrusted networks.
  • Review logs or operational records for repeated failed login attempts.
  • Check whether vendor-recommended mitigations from PSIRT 2021-010 are implemented.
  • Validate access controls with non-disruptive network review, not lockout testing.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-20598 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/aMELSEC iQ-R series CPU modules R08/16/32/120SFCPU; R08/16/32/120PSFCPUall versionsListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.