MiCOM Px40 Advisory: Relay Spare Risk Checks

CISA’s July 9, 2026 advisory for Schneider Electric Easergy MiCOM Px40 Series is a useful reminder that protection relay lifecycle work is not only a firmware or cybersecurity task. For maintenance and MRO teams, the real question is whether the installed relay fleet can be identified, protected, serviced, and replaced without creating a longer outage than the original defect or incident.

The advisory covers CVE-2026-4832, a hard-coded credentials issue that could allow unauthorized access to sensitive device information when an unauthenticated attacker can interrogate the SNMP port. CISA lists the vendor equipment vulnerability score as CVSS v3 5.3. Affected models include multiple Easergy MiCOM Px40 relay families, with version thresholds varying by model family, such as P14x prior to B4A, P24x prior to D3A, P341 prior to E3F, several P342/P343/P344/P345 units prior to B3F, P443/P445/P446/P543/P544/P545/P546 prior to H6A, and other Px40 variants listed in the advisory. CISA describes the product as a protection relay series for medium-voltage, high-voltage, and extra-high-voltage protection.

For customers that do not require SNMP, the advisory directs them to contact Schneider Electric’s Customer Care Center to upgrade firmware to a version without SNMP functionality. Where an upgrade is not applied, or where SNMP is required, the recommended mitigations are operational: use relays only in a protected network environment, separate control networks with firewalls, and use VPN tunnels if remote access is required. CISA states that no known public exploitation specifically targeting this vulnerability had been reported at publication time.

Why a relay advisory changes the spare conversation

Protection relays are not casual panel accessories. They protect feeders, transformers, motors, generators, busbars, and critical electrical assets. If a relay has to be replaced during a fault investigation or planned shutdown, the replacement must match more than the front-panel model name. It needs the right hardware variant, firmware expectations, protection settings, communication configuration, I/O mapping, case style, auxiliary supply, and test documentation.

This is where Schneider Electric automation parts sourcing should be handled with more evidence than a short model line. A relay request should include the exact MiCOM model, firmware or software version if known, serial number, setting file availability, communication protocol use, panel photos, and the site role of the relay. That evidence changes the RFQ from a price request into a controlled replacement path.

SNMP exposure is also an inventory problem

The advisory centers on SNMP interrogation. In practice, many plants do not have a clean list of which relays have SNMP enabled, which ports are reachable, or which engineering workstation or monitoring system polls those devices. A relay may be physically old but logically exposed because it was connected years ago for remote monitoring and never reviewed again.

When teams review communication modules and I/O hardware, include relay communication paths in the same evidence package. The question is not simply whether the relay powers up. It is whether its Ethernet or serial path, protocol settings, and network exposure are understood well enough to harden or replace it without losing visibility or protection coordination.

Firmware action should not outrun outage planning

A firmware recommendation can look simple on paper. In the field, relay firmware work has consequences: settings must be backed up, protection behavior must be validated, test records may be required, and a maintenance window may need approval from operations, electrical engineering, and safety teams. If the relay is part of a critical feeder or substation lineup, unplanned work can create more risk than the advisory response itself.

A practical replacement risk review for obsolete automation parts should therefore separate three cases. First, relays that can be mitigated through network isolation because SNMP is not required. Second, relays that require firmware planning because SNMP remains part of monitoring. Third, relays that should have staged spares because age, availability, or outage criticality makes emergency sourcing unacceptable.

What maintenance teams should collect

Start with installed-base evidence. For each relay, capture model, firmware, serial number, panel location, protected asset, auxiliary power, communication ports in use, protocol, IP address if applicable, SNMP requirement, setting file location, last test date, and spare status. A clear label and wiring workflow such as sending product label photos for model verification is useful, but relay work also needs setting and test context.

If a relay shares auxiliary supply, UPS support, or control power with other panel devices, connect the review to industrial power supply sourcing. Replacing a relay without checking control power, trip circuit health, and panel supply assumptions can create avoidable commissioning problems.

How procurement should frame the RFQ

A good RFQ should state whether the buyer needs an exact spare, a compatible replacement, a firmware evidence review, or an outage-ready package. Include quantity, destination, required lead time, model photos, firmware notes, setting backup status, protected equipment, and whether SNMP or other communication functions are used. If the relay is part of a coordinated protection scheme, say that explicitly. It tells the supplier that interchangeability and documentation matter as much as stock.

FAQ

Does CVE-2026-4832 mean the relay protection function is broken?

The advisory describes unauthorized access to sensitive device information through SNMP interrogation. It should still be treated seriously because relay information, network exposure, and remote access paths can affect operational risk and replacement planning.

Should every MiCOM Px40 relay be upgraded immediately?

No. The correct sequence is inventory, exposure review, SNMP requirement check, firmware/version evidence, and outage planning. Some sites may mitigate through network isolation first while scheduling firmware or replacement work later.

What information is most useful when sourcing a relay spare?

Exact model, firmware, serial number, label photos, panel photos, protected asset, auxiliary supply, communication settings, setting file status, quantity, destination, and outage deadline are all useful. For protection relays, setting and test context matter.

Can a compatible relay replace an older Px40 unit without engineering review?

It should not be assumed. Protection settings, I/O, case style, wiring, firmware behavior, communication protocols, and test procedures must be checked before calling a replacement outage-ready.

Why should procurement care about SNMP?

SNMP tells the buyer whether the relay is only a protective device or also part of the plant’s monitoring architecture. That affects firmware decisions, network isolation, compatibility, and commissioning support.

Practical next step

If your plant is reviewing Easergy MiCOM Px40 relays after this advisory, prepare the installed model list, firmware evidence, SNMP exposure notes, relay photos, setting backup status, protected asset details, spare quantity, destination, and outage window before sourcing. SmartNexMSK can help route the request as exact relay spare sourcing, compatible replacement review, or lifecycle risk planning. Send details to [email protected] or WhatsApp/Phone +86 18259474341.

Source checked: CISA ICS Advisory ICSA-26-190-03, Schneider Electric Easergy MiCOM Px40 Series, July 9, 2026.