CVE-2021-20700
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 · uneditedBuffer overflow vulnerability in the Disk Agent CLUSTERPRO X 4.3 for Windows and earlier, EXPRESSCLUSTER X 4.3 for Windows and earlier, CLUSTERPRO X 4.3 SingleServerSafe for Windows and earlier, EXPRESSCLUSTER X 4.3 SingleServerSafe for Windows and earlier allows attacker to remote code execution via a network.
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 confidenceBuffer overflow vulnerability in the Disk Agent component of NEC's CLUSTERPRO X and EXPRESSCLUSTER X high-availability clustering software for Windows (versions 4.3 and earlier). The flaw is network-exploitable and allows remote attackers to execute arbitrary code without authentication, likely due to insufficient bounds checking when processing network packets.
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>= 1.0, <= 4.3>= 1.0, <= 4.3>= 1.0, <= 4.3>= 1.0, <= 4.3CVSS 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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Confirm NEC clustering software is installedCheck for CLUSTERPRO X or EXPRESSCLUSTER X installation by looking in Program Files, Windows Services, or registry under HKLM\SOFTWARE\NEC or similar. Look for service entries containing 'Clusterpro' or 'Expresscluster'.Affected if The software is found with any version between 1.0 and 4.3 inclusive.
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Identify installed versionUse the product's built-in version information. Check the service properties in Windows Services, the program's About/Version info, or examine the main executable version resource (commonly located in the installation directory under bin or the main product folder).Affected if The version displayed is 4.3 or lower, or any version starting with 1.x through 4.x.
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Verify Disk Agent component statusCheck if the Disk Agent service or component is installed and running. This is typically exposed as a Windows service named 'Disk Agent' or part of the cluster configuration. Check the cluster management console or the service list for 'DiskAgent' or similar naming.Affected if The Disk Agent service is present and running, making the network-facing component active.
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Check network exposure of Disk AgentIdentify the network port the Disk Agent listens on (commonly visible in cluster configuration or service properties). Use 'netstat -an' or Windows Firewall advanced security rules to see if the Disk Agent port is bound to a listening state and accessible from network interfaces.Affected if The Disk Agent is listening on a port accessible from network (not localhost-only or firewalled internally).
You are affected if NEC CLUSTERPRO X or EXPRESSCLUSTER X versions 1.0 through 4.3 are installed with the Disk Agent component enabled and 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.
From vendor dataApply vendor-supplied patches/updates to upgrade to a version beyond 4.3, or implement network segmentation/restrict network access to the Disk Agent service if immediate patching is not feasible.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 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 $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20700 — 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-2021-20700 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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