CVE-2025-40555 Siemens CVE debrief

Who should care

OT/ICS defenders, building automation operators, Siemens APOGEE and TALON TC administrators, and teams responsible for BACnet network segmentation, monitoring, and incident response.

Technical summary

The advisory describes an attacker on the same BACnet network sending a specially crafted BACnet createObject request that triggers continuous unsolicited BACnet broadcast behavior on affected devices. The published CVSS vector is CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L, which aligns with a network-adjacent attack path, no required privileges, no user interaction, and limited availability impact. The primary effect is partial denial of service and reduced BACnet network availability; the issue does not indicate confidentiality or integrity impact in the vector. A power cycle is required to return the device to normal operation.

Defensive priority

Medium. This is not a known emergency exposure like a KEV-listed vulnerability, but it is operationally meaningful for BACnet environments because recovery requires a power cycle and availability of building-control networks can be affected.

Recommended defensive actions

• Identify whether APOGEE PXC+TALON TC Series (BACnet) devices are present in your environment and prioritize them for review.
• Restrict BACnet access to authorized hosts and network segments, especially between building automation zones.
• Monitor for unusual or unsolicited BACnet broadcast traffic and investigate any device that begins emitting unexpected broadcasts.
• Prepare incident response and recovery procedures that account for the need to power-cycle affected devices.
• Review Siemens and CISA advisory materials and apply any vendor guidance if it is updated in the future.

Evidence notes

All substantive statements in this debrief are drawn from the supplied CISA CSAF source item for ICSA-25-135-14 and its referenced Siemens/CISA advisory links. The source states the affected product, attack precondition (same BACnet network), impact (partial denial of service and reduced BACnet availability), recovery requirement (power cycle), CVSS vector, publication date, and that no fix is currently planned.

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.