CVE-2018-7833
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 · uneditedAn Improper Check for Unusual or Exceptional Conditions vulnerability exists in the embedded web servers in all Modicon M340, Premium, Quantum PLCs and BMXNOR0200 where an unauthenticated user can send a specially crafted XML data via a POST request to cause the web server to become unavailable
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 confidenceImproper Check for Unusual or Exceptional Conditions vulnerability in embedded web servers of Modicon M340, Premium, Quantum PLCs and BMXNOR0200 allows unauthenticated remote attackers to send specially crafted XML data via POST request, causing the web server to become unavailable (Denial of Service).
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
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/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 if affected Modicon PLC models are presentInventory your industrial control system (ICS) devices and identify if any of the following models exist: Modicon M340, Modicon Premium, Modicon Quantum, or BMXNOR0200. Check device labeling, network scans, or PLC programming software (like Unity Pro or Control Expert) for model information.Affected if Any of these four Schneider Electric PLC models or communication modules are present in the environment
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Verify the embedded web server is enabledAccess the PLC or BMXNOR0200 module configuration via the programming software (Unity Pro/Control Expert) or the device web interface itself. Check the web server settings or communication module configuration to confirm the embedded web server feature is activated.Affected if The embedded web server (HTTP/HTTPS service) is enabled on the device
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Confirm network accessibility of the web interfaceScan the network for open HTTP/HTTPS ports (typically ports 80, 443, or 8080) on the PLC IP addresses. Review firewall rules, network segmentation, and ACLs to determine if the web server port is reachable from any network segment accessible to untrusted users.Affected if The PLC web server port is reachable from a network segment that contains untrusted or external systems, or is directly accessible via the internet
A user is affected if they have any Modicon M340, Premium, Quantum, or BMXNOR0200 device with the embedded web server enabled and that web interface is accessible from a network path available to unauthenticated users.
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 firmware updates from Schneider Electric to address the vulnerability. Until patches are applied, restrict network access to PLC web interfaces via firewall rules or network segmentation to prevent unauthenticated external access.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 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 $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-7833 — 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-2018-7833 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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