CVE-2021-25909
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 · uneditedZIV Automation 4CCT-EA6-334126BF firmware version 3.23.80.27.36371, allows an unauthenticated, remote attacker to cause a denial of service condition on the device. An attacker could exploit this vulnerability by sending specific packets to the port 7919.
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 confidenceZIV Automation 4CCT-EA6-334126BF controller firmware version 3.23.80.27.36371 contains a denial of service vulnerability on port 7919. An unauthenticated remote attacker can send specially crafted packets to trigger a DoS condition, rendering the device unavailable.
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= 3.23.80.27.36371CVSS 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 device modelAccess the controller's management interface or CLI and retrieve the model identifier. Look for 'ZIV Automation 4CCT-EA6-334126BF' or similar ZIV controller branding in the device information.Affected if The device is NOT a ZIV Automation 4CCT-EA6-334126BF controller - if so, this CVE does not apply.
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Retrieve the firmware versionAccess the controller's management interface, CLI, or system information page. Locate the firmware version field and compare it to '3.23.80.27.36371'.Affected if The firmware version is exactly 3.23.80.27.36371 - other versions are not affected by this specific CVE.
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Verify port 7919 is accessibleFrom a network perspective, determine if port 7919 is open and reachable. This can be done via network scanning (nmap, netcat) from an external host, or by reviewing firewall rules and network exposure configurations.Affected if Port 7919 is exposed to untrusted networks or accessible without authentication - this is required for the exploit to be reachable.
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Confirm service is listening on port 7919From within the device or an adjacent trusted network, attempt to connect to port 7919 (e.g., using telnet, netcat, or a custom client) or check listening services on the device.Affected if A service is actively listening on port 7919 - the vulnerability exists only when the affected service is running.
The environment is affected if it is a ZIV Automation 4CCT-EA6-334126BF controller running firmware version 3.23.80.27.36371 with port 7919 exposed and the service listening.
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 dataRestrict network access to port 7919 using firewall rules or network segmentation to prevent unauthenticated remote access. If available, apply vendor firmware updates. Consider implementing intrusion detection to monitor for anomalous traffic to this port.
- Consultation6.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-25909 — 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-2021-25909 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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