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Modicon M580 FirmwareOperating system · Schneider Electric

CVE-2018-7794

HIGH · 7.5 CVSS v3.1 Published 2020-01-06
Fix available
A fix is available. Upgrade to 2.80 / 3.01 or later.
See remediation →
84/100
Remediation priority · High
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 Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service when reading data with invalid index using Modbus TCP.

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

This is a CWE-754 vulnerability in Schneider Electric Modicon PLCs (M580, M340, Quantum, Premium) where the firmware fails to properly handle exceptional conditions when processing Modbus TCP requests. An attacker can trigger a denial of service by sending Modbus TCP packets that read data using an invalid memory index, causing the device to crash or become unresponsive.

MitigationApply vendor-supplied firmware patches from Schneider Electric for the affected Modicon PLCs. Additionally, restrict network access to Modbus TCP port 502 using firewalls or network segmentation to limit exposure to untrusted networks.

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 M580 FirmwareOperating system
Affected:< 2.80
Modicon M340 FirmwareOperating system
Affected:< 3.01
Tsxh5744m FirmwareOperating system
Affected:< 3.20
Tsxh5724m FirmwareOperating system
Affected:< 3.20
Tsxp576634m FirmwareOperating system
Affected:< 3.20
Tsxp57554m FirmwareOperating system
Affected:< 3.20
Tsxp575634m FirmwareOperating system
Affected:< 3.20
Tsxp57454m FirmwareOperating system
Affected:< 3.20

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
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 checks

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

  1. Identify the Modicon PLC model
    Locate the physical PLC hardware or check the system documentation to identify whether the device is a Modicon M580, M340, or one of the Tsx modules (Tsxh5744m, Tsxh5724m, Tsxp576634m, Tsxp57554m, Tsxp575634m, Tsxp57454m). The model number is typically printed on the front panel of the PLC CPU module.
    Affected if The device is any of the affected models: M580, M340, Tsxh5744m, Tsxh5724m, Tsxp576634m, Tsxp57554m, Tsxp575634m, or Tsxp57454m.
  2. Check the installed firmware version
    Access the PLC programming software (Unity Pro or EcoStruxure Control Expert), connect to the PLC, and navigate to the CPU properties or system information to view the firmware version. Alternatively, check the sticker on the CPU module which often displays the firmware version.
    Affected if The firmware version is below 2.80 for M580, below 3.01 for M340, or below 3.20 for any Tsx module listed.
  3. Verify if Modbus TCP is enabled
    In the PLC programming software, check the PLC configuration settings to determine if Modbus TCP communication is enabled. This is typically found in the communication configuration or network settings. Look for Modbus TCP or Ethernet IP settings.
    Affected if Modbus TCP is enabled on the PLC, as this is the protocol through which the malformed requests are sent.
  4. Assess network exposure of Modbus TCP port 502
    Scan the network to determine if port 502 (Modbus TCP) is accessible from network segments that contain untrusted or external systems. Use a network scanner or firewall logs to identify exposure. Check if the PLC is directly accessible from the corporate network or the internet.
    Affected if Port 502 is accessible from untrusted network segments, increasing the likelihood of an external attacker being able to send malicious Modbus TCP packets.

A user is affected if they have a vulnerable Modicon PLC model (M580, M340, or the listed Tsx modules) with a firmware version below the thresholds (2.80, 3.01, or 3.20 respectively) AND Modbus TCP is enabled and network-accessible.

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 2.80 / 3.01 / 3.20 or later
Fixed in 2.803.013.20
Interim mitigation

Apply vendor-supplied firmware patches from Schneider Electric for the affected Modicon PLCs. Additionally, restrict network access to Modbus TCP port 502 using firewalls or network segmentation to limit exposure to untrusted networks.

Fix this in Modicon M580 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2018-7794 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