CVE-2025-40944

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-13 · updated 2026-06-17
Weakness: CWE-400

Description

A vulnerability has been identified in SIMATIC ET 200AL IM 157-1 PN (6ES7157-1AB00-0AB0) (All versions), SIMATIC ET 200MP IM 155-5 PN HF (6ES7155-5AA00-0AC0) (All versions >= V4.2.0), SIMATIC ET 200SP IM 155-6 MF HF (6ES7155-6MU00-0CN0) (All versions), SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) (All versions < V1.3), SIMATIC ET 200SP IM 155-6 PN R1 (6ES7155-6AU00-0HM0) (All versions < V6.0.1), SIMATIC ET 200SP IM 155-6 PN/2 HF (6ES7155-6AU01-0CN0) (All versions >= V4.2.0 < V4.2.5), SIMATIC ET 200SP IM 155-6 PN/3 HF (6ES7155-6AU30-0CN0) (All versions < V4.2.2), SIMATIC PN/MF Coupler (6ES7158-3MU10-0XA0) (All versions), SIMATIC PN/PN Coupler (6ES7158-3AD10-0XA0) (All versions < V6.0.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-2AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-7AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL (6AG2155-5AA00-1AC0) (All versions >= V4.2.0), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-2CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-7CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL (6AG2155-6AU01-1CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF TX RAIL (6AG2155-6AU01-4CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS NET PN/PN Coupler (6AG2158-3AD10-4XA0) (All versions < V6.0.0). Affected devices do not properly handle S7 protocol session disconnect requests. When receiving a valid S7 protocol Disconnect Request (COTP DR TPDU) on TCP port 102, the devices enter an improper session state. This could allow an attacker to cause the device to become unresponsive, leading to a denial-of-service condition that requires a power cycle to restore normal operation.

Affected products

Siemens SIMATIC ET 200AL IM 157-1 PN: all versions
Siemens SIMATIC ET 200MP IM 155-5 PN HF: from V4.2.0
Siemens SIMATIC ET 200SP IM 155-6 MF HF: all versions
Siemens SIMATIC ET 200SP IM 155-6 PN/2 HF: from V4.2.0 before V4.2.5 — fixed in V4.2.5
Siemens SIMATIC ET 200SP IM 155-6 PN/3 HF: before V4.2.2 — fixed in V4.2.2
Siemens SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants): before V1.3 — fixed in V1.3
Siemens SIMATIC ET 200SP IM 155-6 PN R1: before V6.0.1 — fixed in V6.0.1
Siemens SIMATIC PN/MF Coupler: all versions
Siemens SIMATIC PN/PN Coupler: before V6.0.0 — fixed in V6.0.0
Siemens SIPLUS ET 200MP IM 155-5 PN HF: from V4.2.0
Siemens SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL: from V4.2.0
Siemens SIPLUS ET 200SP IM 155-6 PN HF: from V4.2.0 before V4.2.5 — fixed in V4.2.5
Siemens SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL: from V4.2.0 before V4.2.5 — fixed in V4.2.5
Siemens SIPLUS ET 200SP IM 155-6 PN HF TX RAIL: from V4.2.0 before V4.2.5 — fixed in V4.2.5
Siemens SIPLUS NET PN/PN Coupler: before V6.0.0 — fixed in V6.0.0

How to fix

Upgrade to a fixed version: Siemens SIMATIC ET 200SP IM 155-6 PN/2 HF V4.2.5; Siemens SIMATIC ET 200SP IM 155-6 PN/3 HF V4.2.2; Siemens SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) V1.3; Siemens SIMATIC ET 200SP IM 155-6 PN R1 V6.0.1; Siemens SIMATIC PN/PN Coupler V6.0.0; Siemens SIPLUS ET 200SP IM 155-6 PN HF V4.2.5; Siemens SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL V4.2.5; Siemens SIPLUS ET 200SP IM 155-6 PN HF TX RAIL V4.2.5; Siemens SIPLUS NET PN/PN Coupler V6.0.0. Check the vendor advisory for mitigations.

References

https://cert-portal.siemens.com/productcert/html/ssa-674753.html

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