CVE-2018-7846 Schneider Electric CVE debrief

Who should care

OT/ICS operators, plant engineers, and defenders responsible for Schneider Electric Modicon M580, M340, Quantum, Quantum Safety, or Premium controllers, especially where Modbus/TCP access and controller management are allowed on production networks.

Technical summary

The source advisory characterizes the issue as a trust boundary violation on controller connection that may permit unauthorized access by brute-force activity against Modbus. The CISA CSAF record identifies affected firmware families including Modicon M580 firmware prior to v2.90, M340 firmware prior to v3.10, and all versions of Quantum, Quantum Safety, and Premium firmware in the referenced controller lines. The record’s CVSS v3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L, indicating a network-reachable issue with limited availability impact in that scoring model. Remediation is product-specific: M580 has a fix in SV4.20 or above, and M340 has a fix in v3.60 or above, with accompanying guidance to set an application password, align project firmware settings, rebuild, and transfer projects. Quantum and Premium are listed as end-of-life with no fix planned in the advisory, so mitigation and migration are the recommended path.

Defensive priority

Medium overall, but higher priority in environments where Modbus/TCP is reachable across weakly segmented OT networks or where controller access controls are not already in place. Prioritize fixed-version upgrades for M580/M340 and compensating controls plus migration planning for Quantum/Premium.

Recommended defensive actions

• Upgrade Modicon M580 to firmware SV4.20 or above and EcoStruxure Control Expert to v16.0, then set an application password, update the controller firmware version in the project, rebuild, and transfer the project.
• Upgrade Modicon M340 to firmware v3.60 or above and EcoStruxure Control Expert to v16.0 or later, then set an application password, update the project firmware setting, rebuild, and transfer the project.
• Restrict Modbus/TCP exposure by segmenting networks and blocking unauthorized access to port 502/TCP with firewalls and access-control lists.
• Use the vendor-recommended secure communications guidance, including IPsec-oriented options where applicable, to reduce trust-boundary exposure on controller connections.
• For Quantum, Quantum Safety, and Premium controllers, plan migration because the advisory states these products are end of life and no fix is planned; apply compensating controls in the meantime.
• Inventory affected controllers and verify both firmware versions and project configuration to ensure the deployed controller matches the remediated target version.

Evidence notes

The description in the source corpus states: "A trust boundary violation vulnerability on connection to the controller exists which could cause unauthorized access by conducting a brute force attack on Modbus protocol to the controller." The CSAF source item ties the issue to Schneider Electric Modicon controllers and lists affected products and fixes. Remediation entries explicitly name M580 SV4.20+ and M340 v3.60+ as fixes, while Quantum and Premium are marked end of life with no fix planned. The revision history in the CSAF record shows later updates, including 2019-08-13, 2020-10-12, and 2020-12-08, which is useful for advisory context but not for the CVE issue date. The supplied CVE metadata also contains a CVSS v4.0 statement in the description while the source item records a CVSS v3.1 vector; both are part of the supplied corpus.

Official resources