CVE-2021-34566
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 · uneditedIn WAGO I/O-Check Service in multiple products an unauthenticated remote attacker can send a specially crafted packet containing OS commands to crash the iocheck process and write memory resulting in loss of integrity and DoS.
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 confidenceWAGO I/O-Check Service contains a vulnerability allowing unauthenticated remote attackers to send specially crafted packets containing OS commands. This enables both denial of service (crashing the iocheck process) and memory integrity compromise through arbitrary memory writes.
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< 18= 18< 18= 18< 18= 18< 18= 18< 18= 18< 18= 18< 18= 18< 18= 18CVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 the WAGO device modelLocate the device label or check the device configuration to confirm the specific WAGO 750 series model (e.g., 750-8100, 750-8101, 750-8102, 750-8202)Affected if The device model matches one of the affected models: 750-8100, 750-8101, 750-8101/025 000, 750-8102, 750-8102/025 000, 750-8202, 750-8202/000 011, or 750-8202/000 012
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Check the installed firmware versionAccess the WAGO device web interface, use WAGO Tool or check the device system information to retrieve the firmware version numberAffected if The firmware version is less than 18 or exactly version 18
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Verify if the I/O-Check Service is accessibleCheck if the I/O-Check Service (typically listens on port 6626/TCP or 6627/TCP) is exposed to the network or reachable from untrusted networksAffected if The I/O-Check Service port is open and accessible from network segments that contain untrusted devices
A user is affected if they are running any of the listed WAGO 750 series devices with firmware version 18 or lower, and the I/O-Check Service is network-accessible.
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.
dbcve · scoped18
Apply vendor-provided patches for affected WAGO products and implement network segmentation to restrict access to the I/O-Check Service to trusted sources only.
WAGO 750 series firmware > version 18 (contact WAGO for specific fixed version)
- 1. Identify the specific WAGO 750 series device model in your environment
- 2. Download the latest firmware version from the official WAGO website or contact WAGO support
- 3. Follow WAGO's official firmware update procedure, typically involving the WAGO Ethernet Settings software or Web-Based Management interface
- 4. Verify the firmware version after upgrade to confirm it is beyond version 18
- 5. Test the iocheck service functionality after the upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $11,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-34566 — 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-2021-34566 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
- No spam, self-promotion, credentials, or personal data