CVE-2020-7543
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 Improper Check for Unusual or Exceptional Conditions vulnerability in Modicon M580, M340, Quantum, and Premium controllers allows denial of service via specially crafted Read Physical Memory requests sent over the Modbus protocol. The vulnerability stems from insufficient validation of exceptional conditions when processing malformed memory read commands, causing the controller to fail or become unresponsive.
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 modelLocate the controller hardware label or check the system configuration to confirm the exact model number (e.g., Bmep584040, Bmep582040, etc.)Affected if The model is one of the listed M580 variants: Bmep584040, Bmep582040, Bmep586040, Bmep585040, Bmep582020, Bmep581020, or Bmep583040
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Check the installed firmware versionAccess the controller firmware revision through the engineering workstation software (Unity Pro or EcoStruxure) or the controller's web interface if available, and note the exact firmware version numberAffected if The firmware version is below 3.20 (e.g., 3.10, 2.x, etc.)
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Verify Modbus protocol is enabledCheck the controller's communication configuration settings in the programming software to confirm Modbus TCP or Modbus serial is configured and activeAffected if Modbus protocol is enabled and the controller is reachable over the network
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Confirm network exposure of Modbus serviceReview network segmentation and firewall rules to determine if the Modbus port (typically TCP 502) is accessible from unauthorized or external network segmentsAffected if The Modbus service is accessible from network segments that contain non-authorized systems
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Assess ability to send Read Physical Memory commandsDetermine if external systems have the capability to send Modbus function code 0x2B (Read Physical Memory) to the controller - this may require reviewing access control lists or using a Modbus client to test connectivityAffected if External or unauthorized systems can send Modbus commands to the controller
A user is affected if they have a Modicon M580 controller from the listed models running firmware version below 3.20 with Modbus enabled and accessible, as the vulnerability can be triggered by specially crafted Read Physical Memory requests.
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 the vendor-supplied firmware update from Schneider Electric that addresses this vulnerability, and implement network segmentation to restrict Modbus access to authorized systems only.
- Consultation6.0 h
- Implementation10.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-7543 — 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-2020-7543 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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