CVE-2021-37401
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 · uneditedAn attacker may obtain the user credentials from file servers, backup repositories, or ZLD files saved in SD cards. As a result, the PLC user program may be uploaded, altered, and/or downloaded.
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 · moderate confidenceAuthentication bypass vulnerability in PLC (Programmable Logic Controller) systems where user credentials can be extracted from unsecured file servers, backup repositories, or ZLD files stored on SD cards. Successful exploitation allows attackers to upload, modify, or download PLC user programs, compromising industrial control operations.
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<= 2.12.1<= 1.3.1<= 8.19.1<= 2.31<= 1.91<= 2.31<= 2.32<= 2.31CVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Idec software versionsCheck the installed version of Idec Data File Manager, Windedit, or Windldr by accessing the software's About or Help menu, or checking the program's file properties. For PLC firmware, access the device configuration or system information page via the programming interface.Affected if The version number is at or below the affected threshold (Data File Manager <= 2.12.1, Windedit <= 1.3.1, Windldr <= 8.19.1) or firmware versions are at or below the listed limits.
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Locate ZLD backup files on accessible storageSearch for .zld file extensions on networked file servers, local hard drives, backup repositories, and any mounted SD cards used with PLC equipment. Check common backup directories and removable media.Affected if ZLD files containing PLC program data and credentials are found in locations with weak or no access controls.
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Inspect SD card contents on PLC devicesExamine any SD cards used with Idec Microsmart or Ft1a controllers. Read the card directly on a workstation to inspect the file structure and identify stored configuration or backup files.Affected if SD cards contain unencrypted ZLD files or backup data that could expose credentials.
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Review backup repository access controlsAudit file shares, backup folders, or version control repositories where PLC project files, backups, or exports are stored. Verify who has read or write access to these locations.Affected if Backup repositories are accessible to unauthorized users or use weak/no authentication.
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Check for credential exposure in project filesOpen any retrieved ZLD or backup files in a hex editor or text viewer to look for stored username and password strings. Many PLC systems store credentials in plain text or weakly encoded format in these files.Affected if User credentials or authentication tokens are found in plain text within backup or project files.
A defender is affected if any Idec software or firmware version falls within the affected ranges AND unsecured backup files, ZLD files on SD cards, or accessible repositories containing PLC project data are present in the environment.
Generated from the published advisory. Verify against your own configuration.
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 dataSecure credential storage locations by implementing encryption at rest, restrict access to backup repositories and SD card files, rotate exposed credentials immediately, and apply vendor-provided patches for the affected PLC systems.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-37401 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-37401 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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