CVE-2020-7535
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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal' Vulnerability Type) vulnerability exists in the Web Server on Modicon M340, Legacy Offers Modicon Quantum and Modicon Premium and associated Communication Modules (see security notification for affected versions), that could cause disclosure of information when sending a specially crafted request to the controller over HTTP.
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 path traversal vulnerability (CWE-22) in the web server component of Modicon M340, Modicon Quantum, and Modicon Premium PLCs allows remote attackers to access restricted directories and disclose sensitive files on the controller via specially crafted HTTP requests without proper path sanitization.
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< 3.30< 3.30< 3.30< 3.30< 3.30< 3.30< 3.30< 3.4CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 PLC model numberLocate the model number label on the physical PLC hardware or check the device inventory/asset management system. Look for model numbers such as Bmxp341000, Bmxp342000, Bmxp3420102, Bmxp3420102cl, Bmxp342020, Bmxp3420302, Bmxp3420302cl, or Bmxnoe0100.Affected if The model matches one of the affected models listed in the CVE.
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Determine the installed firmware versionAccess the PLC through Schneider Electric's programming software (such as Unity Pro or EcoStruxure Control Expert) and navigate to the firmware version information, or query the device via its web interface if available. For network-accessible devices, you may also retrieve the version from the HTTP server banner or SNMP device information.Affected if The firmware version is below 3.30 for Modicon M340 models or below 3.4 for Bmxnoe0100.
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Verify if the web server is enabledCheck the PLC configuration in the programming software under the network module settings, or attempt to access the device via HTTP on port 80 or 443. If the web server responds to HTTP requests, it is enabled.Affected if The web server component is active and responding to HTTP requests.
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Confirm path traversal is possibleSend a crafted HTTP GET request containing traversal sequences such as ../ to the web server endpoint, for example: GET /..//..//..//etc/passwd HTTP/1.1 or similar patterns. Observe if the response includes content from restricted directories.Affected if The web server returns sensitive file contents or directory listings that should not be accessible.
A user is affected if they have a Modicon M340 or Bmxnoe0100 PLC with web server enabled and firmware version below 3.30 (or 3.4 for Bmxnoe0100), and the device is accessible via network without proper access controls.
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 data3.43.30
Restrict network access to the controller's web server using network segmentation and firewall rules, implement input validation on HTTP requests to block traversal sequences (../), and apply vendor-provided firmware updates. If patching is not immediately feasible, disable the web server if not required for operations.
- Consultation8.0 h
- Implementation12.0 h
- Testing8.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-7535 — 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-2020-7535 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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