TCP Sequence Number Validation Bypass in Siemens Interniche IP-Stack

Successful exploitation can disrupt TCP connection establishment or handling, resulting in denial of service against affected TCP-based services. Available information indicates the primary impact is on availability; confidentiality and integrity impacts are not described as affected. Because the flaw can be triggered remotely by an unauthenticated attacker under the right network conditions, exposed industrial services may become unreliable or unavailable.

Reduce exposure of affected devices to untrusted networks, restrict access to TCP-based services to trusted hosts and network segments, and implement network filtering to block spoofed IP packets where possible. Siemens and CISA also recommend defense-in-depth measures for industrial environments, including network isolation of control systems, minimizing direct Internet exposure, using secure remote access methods such as VPNs, and monitoring for anomalous network traffic. For some affected deployments, Siemens recommends product-specific workarounds such as limiting TCP accessibility to trusted IP addresses and using alternative communication configurations where documented.

Apply Siemens-provided security updates or upgrade to vendor-recommended fixed versions for affected products where patches are available. For products for which Siemens has announced no security update, follow vendor-recommended compensating controls and lifecycle management guidance, including migration away from unsupported platforms where feasible.