CVE-2018-7845 Schneider Electric CVE debrief

Who should care

OT security teams, PLC/controls engineers, plant operators, and asset owners running Schneider Electric Modicon M580, M340, Quantum, or Premium controllers and their associated firmware, especially where Modbus access is available on port 502/TCP.

Technical summary

The supplied advisory describes an out-of-bounds read condition in controller memory handling over Modbus. An attacker who can reach the affected service may be able to read past intended memory bounds and disclose unexpected data from the controller. The CISA CSAF source lists impacted Schneider Electric Modicon firmware families and recommends firmware updates plus network-level mitigations such as segmentation, ACLs, and blocking unauthorized access to Modbus on TCP/502.

Defensive priority

High. Prioritize remediation where affected controllers are reachable from broader OT networks or any untrusted segment, and especially where Modbus access is not tightly controlled.

Recommended defensive actions

• Update affected Schneider Electric firmware to the vendor-fixed release for the specific platform: M580 sv4.20 or above, M340 v3.60 or above, Quantum v3.60, or Premium v3.20, as applicable.
• If firmware update is not immediately possible, restrict Modbus access on TCP/502 with segmentation and firewall rules so only authorized engineering assets can connect.
• Apply the vendor-recommended access control list settings and application password protections in project properties.
• Rebuild and transfer updated projects in EcoStruxure Control Expert after changing controller firmware versions, as directed in the advisory.
• For Quantum and Premium systems noted as end of life, plan migration to supported platforms and use the vendor mitigation guidance in the interim.
• Review whether any affected controllers are exposed beyond the OT trust boundary and remove unnecessary paths to Modbus services.

Evidence notes

The source corpus states that an out-of-bounds read could disclose unexpected data from the controller when reading specific memory blocks over Modbus. It also lists affected Schneider Electric Modicon M580, M340, Quantum, and Premium firmware variants and provides vendor fixes and mitigations, including firmware upgrades, application passwords, ACLs, segmentation, and blocking unauthorized access to port 502/TCP. The advisory notes that some Quantum and Premium products are end of life and should be migrated where possible.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.