CVE-2025-40556 Denial of service in BACnet ATEC 550-440
An attacker on the same BACnet network can cause a denial of service on Siemens ATEC devices by sending crafted MSTP messages, requiring a power cycle to recover.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-40556?
CVE-2025-40556 is a high-severity denial of service vulnerability in Siemens BACnet ATEC 550-440, published on 13 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A vulnerability has been identified in BACnet ATEC 550-440 (All versions), BACnet ATEC 550-441 (All versions), BACnet ATEC 550-445 (All versions), BACnet ATEC 550-446 (All versions). Affected devices improperly handle specific incoming BACnet MSTP messages. This could allow an attacker residing in the same BACnet network to send a specially crafted MSTP message that results in a denial of service condition of the targeted device. A power cycle is required to restore the device's normal operation.
Weakness: CWE-20
Which versions are affected by CVE-2025-40556?
How do I fix CVE-2025-40556?
No fix has been published for CVE-2025-40556 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-40556 being exploited?
There is no known exploitation of CVE-2025-40556 in the wild and no public exploit code.
Sources
Also known as GHSA-c7rq-qv3j-63j3.