Critical Siemens Flaw CVE-2025-40771 (CVSS 9.8) Allows Unauthenticated Remote Access to SIMATIC CP Config

Siemens has disclosed a critical vulnerability, CVE-2025-40771 (CVSS 9.8), that could allow an unauthenticated remote attacker to access configuration data on SIMATIC CP devices. The flaw affects SIMATIC ET 200SP communication processors, specifically CP 1542SP-1, CP 1542SP-1 IRC and CP 1543SP-1 (including SIPLUS variants), with all versions prior to V2.4.24. Siemens has released fixed firmware versions V2.4.24 and later for all affected models.

The vulnerability arises because the devices do not properly authenticate configuration connections, enabling unauthenticated remote access to configuration data on the network. According to Siemens, the issue stems from CWE-306: Missing Authentication for Critical Function.

The company urges customers to update and, if patching is not immediately possible, to restrict access to the affected systems to trusted IP addresses only and follow its operational security guidelines for isolating devices and enforcing strong access controls.