CVE-2021-38395
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 · uneditedHoneywell Experion PKS C200, C200E, C300, and ACE controllers are vulnerable to improper neutralization of special elements in output, which may allow an attacker to remotely execute arbitrary code and cause a denial-of-service condition.
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 confidenceThe vulnerability affects Honeywell Experion PKS C200, C200E, C300, and ACE controllers. It involves improper neutralization of special elements in output, which could allow an attacker to inject malicious input that gets processed by the controller, leading to remote code execution and denial-of-service conditions.
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 dataall versionsall versionsall versionsall versionsCVSS 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 Honeywell Experion PKS controllers on the networkScan the network for devices with Honeywell vendor OUI (MAC addresses starting with 00:1D:9C or similar), or check network documentation for C200, C200E, C300, or ACE controller deployments. Use Nmap or network scanning tools to identify devices responding to typical industrial protocols on ports 443, 4444, or 5555.Affected if Any Honeywell C200, C200E, C300, or ACE controller is found on the network
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Confirm controller model and firmware versionAccess the controller management interface (typically via web browser to the controller IP, or console connection) and navigate to the system information or firmware version page. Record the exact model number (C200, C200E, C300, or ACE) and firmware version displayed.Affected if The identified controller matches any of the affected models (C200, C200E, C300, or ACE) regardless of firmware version since all versions are affected
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Check for exposed management interfacesPerform a port scan on the controller IP address using Nmap or similar tool. Look for open ports associated with Experion management (typically TCP 443 for HTTPS web interface, TCP 4444 for controller communication). Verify if these interfaces are accessible from network segments outside the control system DMZ.Affected if Management interfaces (web UI on port 443, control ports on 4444/5555) are exposed to network segments beyond the control system security zone
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Identify input injection pointsReview controller configuration for enabled input channels: check if Serial/Modbus ports, OPC interfaces, or web-based configuration forms are active. Use controller documentation or configuration backup to enumerate active communication protocols and data input paths.Affected if Any network-accessible input channel (web forms, Modbus/OPC interfaces, serial communications) is enabled and accepts external data without documented input validation
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Verify network segmentation of controllerReview network firewall rules, VLAN configurations, or ACLs protecting the controller. Check if the controller has direct connectivity to corporate networks, the internet, or untrusted zones. Use network diagrams or firewall rule review to map traffic paths to the controller.Affected if Controller has direct network path from untrusted network segments (corporate LAN, internet) without intermediate security controls
A user is affected if any Honeywell Experion PKS C200, C200E, C300, or ACE controller is present on their network with management or input interfaces exposed to potentially untrusted network segments.
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 for Experion PKS controllers; if unavailable, implement network segmentation to isolate controllers and restrict external access to management interfaces.
- Consultation8.0 h
- Implementation4.0 h
- Testing12.0 h
- Review / QA6.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-38395 — 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-2021-38395 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
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