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Modicon M340 Bmxp341000 FirmwareOperating system · Schneider Electric

CVE-2020-7549

MEDIUM · 5.3 CVSS v3.1 Published 2020-12-11
Fix available
A fix is available. Upgrade to 3.4 / 3.30 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
A CWE-754: Improper Check for Unusual or Exceptional Conditions 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 denial of HTTP and FTP services when a series of specially crafted requests is sent 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 · moderate confidence

A denial of service vulnerability exists in the Web Server component of Modicon M340, Modicon Quantum, and Modicon Premium PLCs. The issue stems from improper handling of unusual or exceptional conditions (CWE-754), allowing attackers to crash HTTP and FTP services by sending specially crafted HTTP requests.

MitigationApply the firmware update from Schneider Electric's security notification. Until patched, consider network segmentation to limit exposure and monitor for signs of service degradation.

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
Modicon M340 Bmxp341000 FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp342000 FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp3420102 FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp3420102cl FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp342020 FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp3420302 FirmwareOperating system
Affected:< 3.30
Modicon M340 Bmxp3420302cl FirmwareOperating system
Affected:< 3.30
Bmxnoe0100 FirmwareOperating system
Affected:< 3.4

CVSS 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
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the Modicon PLC model
    Locate the PLC hardware and read the model number label. Look for model identifiers such as Bmxp341000, Bmxp342000, Bmxp3420102, Bmxp3420102cl, Bmxp342020, Bmxp3420302, Bmxp3420302cl, or Bmxnoe0100. This information is typically printed on the CPU module or available in the programming software project properties.
    Affected if The PLC model matches one of the affected models listed in the CVE.
  2. Determine the firmware version
    Using Schneider Electric's programming software (such as Unity Pro or EcoStruxure Control Expert), connect to the PLC and retrieve the firmware version from the CPU module properties. Alternatively, access the PLC's web interface if available and check the system information page. Compare your firmware version against the affected ranges: M340 models require firmware < 3.30, and Bmxnoe0100 requires firmware < 3.4.
    Affected if The installed firmware version is below 3.30 for Modicon M340 models or below 3.4 for Bmxnoe0100.
  3. Verify if the Web Server is enabled
    Access the PLC configuration through the programming software and check the network services configuration. Look for settings related to HTTP and FTP server enablement. On the web interface, confirm whether HTTP or FTP services are active. This is typically found under the PLC's network configuration or web server settings.
    Affected if HTTP and/or FTP web server services are enabled and running on the PLC.
  4. Assess network exposure
    Review the network topology and firewall rules to determine if the PLC's HTTP (port 80/443) and FTP (port 21) services are accessible from untrusted networks. Check if the PLC is directly connected to the internet or resides in an unsegmented network zone.
    Affected if The PLC's web server ports are accessible from networks outside the trusted control system network.

The PLC is affected if it is a Modicon M340 model with firmware below 3.30 or a Bmxnoe0100 with firmware below 3.4, and the HTTP or FTP web server is enabled and exposed on the network.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 3.4 / 3.30 or later
Fixed in 3.43.30
Interim mitigation

Apply the firmware update from Schneider Electric's security notification. Until patched, consider network segmentation to limit exposure and monitor for signs of service degradation.

Fix this in Modicon M340 Bmxp341000 Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,448.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-7549 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data