ICSA-25-352-05: Siemens Interniche IP-Stack

CISA's summary

Summary: Multiple Industrial products are affected by a vulnerability in the Interniche IP-Stack. The 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. Siemens has released new versions for several affected products and recommends to update to the latest versions. Siemens is preparing further fix versions and recommends specific countermeasures for products where fixes are not, or not yet available.

Products, as the advisory lists them

DeSpy has not checked any unit, hardware revision or firmware.

Vulnerabilities in this advisory

• CVE-2025-40820 — CVE-2025-40820 · CWE-940

  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.

Acknowledgments, as the advisory lists them

• Siemens ProductCERT: reported this vulnerability to CISA.
• Qian Zou, Xuewei Feng, Ke Xu, Qi Li, Xueying Li, Gang Jin, Zhongguancun Laboratory: reported this vulnerability to Siemens
• Tsinghua University: reported this vulnerability to Siemens

The advisory's legal notice

The use of Siemens Security Advisories is subject to the terms and conditions listed on: https://www.siemens.com/productcert/terms-of-use.

Sources

• The advisory at cisa.gov
• The CSAF document (JSON)

DeSpy's copy of this version is dated 2026-09-28.