CVE-2025-40820: Siemens Sidoor ATD430W

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

Affected products do not properly enforce TCP sequence number validation in specific scenarios but accept values within a broad range. This could allow an unauthenticated remote attacker e.g. to interfere with connection setup, potentially leading to a denial of service. The attack succeeds only if an attacker can inject IP packets with spoofed addresses at precisely timed moments, and it affects only TCP-based services.

Affected products

Siemens Sidoor ATD430W: any version
Siemens Sidoor ATE530G Coated: any version
Siemens Sidoor ATE530S Coated: any version
Siemens SIMATIC Cfu Diq: before V2.0.0 (fixed in V2.0.0)
Siemens SIMATIC Cfu Pa: before V2.0.0 (fixed in V2.0.0)
Siemens SIMATIC Et 200al Im 157-1 Pn: any version
Siemens SIMATIC Et 200clean, Cm 8x Io-Link: any version
Siemens SIMATIC Et 200clean, Di 16x24vdc: any version
Siemens SIMATIC Et 200clean, Diq 16x24vdc/0,5a: any version
Siemens SIMATIC Et 200eco Pn, Ai 8xrtd/tc, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Cm 4x Io-Link, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Cm 8x Io-Link, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Di 16x24vdc, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Di 8x24vdc, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Diq 16x24vdc/2a, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Dq 8x24vdc/0,5a, m12-L: from V5.1.1
Siemens SIMATIC Et 200eco Pn, Dq 8x24vdc/2a, m12-L: from V5.1.1
Siemens SIMATIC Et 200mp Im 155-5 Pn Hf: from V4.2.0
Siemens SIMATIC Et 200pro Im 154-8 Pn/dp CPU: any version
Siemens SIMATIC Et 200pro Im 154-8f Pn/dp CPU: any version
Siemens SIMATIC Et 200pro Im 154-8fx Pn/dp CPU: any version
Siemens SIMATIC Et 200s Im 151-8 Pn/dp CPU: any version
Siemens SIMATIC Et 200s Im 151-8f Pn/dp CPU: any version
Siemens SIMATIC Et 200sp CPU 1510sp-1 Pn: any version
Siemens SIMATIC Et 200sp CPU 1510sp F-1 Pn: any version
and 120 more

Published 2025-12-09. Last modified 2026-10-07.