CVE-2020-7537
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 · uneditedA CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Legacy Controllers Modicon Quantum & Modicon Premium (see security notifications for affected versions), that could cause denial of service when a specially crafted Read Physical Memory request over Modbus is sent to the controller.
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 confidenceA CWE-754 vulnerability exists in Schneider Electric Modicon controllers (M580, M340, Quantum, Premium) where improper handling of unusual or exceptional conditions in the Modbus protocol's Read Physical Memory request processing allows an attacker to cause denial of service by sending specially crafted requests.
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< 3.20< 3.20< 3.20< 3.20< 3.20< 3.20< 3.20< 3.20CVSS 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 Modicon controller modelAccess the controller's web interface, Unity Pro programming software, or check the physical device label to determine the exact model number (e.g., Bmep584040, Bmep582040, etc.)Affected if The model is one of the affected M580 variants (Bmep584040, Bmep582040, Bmep586040, Bmep585040, Bmep582020, Bmep581020, Bmep584020, Bmep583040)
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Check the installed firmware versionUse the controller's web interface, Unity Pro/Control Expert software, or query the device via Modbus function code 0x2B/0x0E (Device Identity) to retrieve the firmware versionAffected if The firmware version is below 3.20 (e.g., 3.10, 3.0, 2.x)
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Verify Modbus protocol is enabledCheck the controller configuration in Unity Pro/Control Expert under Communication > Modbus TCP settings, or examine the network services list on the controller's web interfaceAffected if Modbus/TCP (port 502) or Modbus Serial is enabled and listening for requests
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Assess network exposureScan the network to determine if port 502 (Modbus TCP) is accessible from non-trusted network segments, or review firewall rules and network segmentation policiesAffected if Port 502 is open to untrusted networks or the controller is not isolated on a segmented OT network
You are affected if you have a vulnerable M580 model with firmware below 3.20 and Modbus is network-accessible from your corporate or external networks.
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 data3.20
Apply vendor-supplied firmware patches for affected Modicon controllers and implement network segmentation to isolate ICS/OT assets from untrusted networks, as this Modbus-based DoS is network-exploitable.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-7537 — 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-2020-7537 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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- Version or environment caveats, and links to real fixes
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