CVE-2021-21000
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 · uneditedOn WAGO PFC200 devices in different firmware versions with special crafted packets an attacker with network access to the device could cause a denial of service for the login service of the runtime.
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 confidenceA denial of service vulnerability in WAGO PFC200 devices allows an unauthenticated remote attacker with network access to send specially crafted packets that crash the login service of the runtime, preventing legitimate users from authenticating to the device.
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< fw08< fw15< fw15< fw08< fw15< fw08< fw16< fw15CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 the PFC200 device model and part numberAccess the device web interface, check the device label, or run a system info command via SSH or management console to identify the 750-xxx part number (e.g., 750-823, 750-829, 750-831, 750-832, 750-852, 750-862, 750-880, or 750-881)Affected if The device is a WAGO PFC200 with a part number matching 750-823, 750-829, 750-831, 750-832, 750-852, 750-862, 750-880, or 750-881
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Determine the installed firmware versionLog into the device via web interface, SSH, or management console and locate the firmware version information, typically found under System > Firmware, Device Info, or About sectionsAffected if The installed firmware version is below fw08 for 750-823/750-832/750-862, below fw15 for 750-829/750-831/750-852/750-881, or below fw16 for 750-880
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Verify the login service is operationalAttempt to access the device login page via HTTP/HTTPS or test authentication via SSH. Check device logs or status indicators for any recent login service crashes or unavailabilityAffected if The login service is unresponsive, crashes repeatedly, or logs indicate login service failures since the device was last patched
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Assess network exposure of management interfacesReview firewall rules, network segmentation, and access control lists to determine if ports used for device management (HTTP/HTTPS, SSH) are exposed to untrusted networks or the internetAffected if Management interfaces are reachable from untrusted networks or the internet without proper network segmentation
The device is affected if it is a WAGO PFC200 with a matching part number and its firmware version falls below the threshold specified for that model, and the login service can be reached by an unauthenticated remote attacker.
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 dataApply network segmentation to restrict access to the PFC200 management interfaces and monitor for availability of the login service. Contact WAGO for firmware updates that address this vulnerability.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21000 — 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-2021-21000 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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- 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
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