Siemens Industrial Products Vulnerable to TCP Sequence Validation Flaw in Interniche IP-Stack

Siemens Industrial Products Affected by Interniche IP-Stack Vulnerability

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has issued an advisory (ICSA-25-352-05) warning of a critical vulnerability in Siemens industrial products utilizing the Interniche IP-Stack. The flaw, which involves improper TCP sequence number validation, could allow unauthenticated remote attackers to exploit affected systems under specific conditions.

Technical Details

The vulnerability stems from the affected products' failure to enforce strict TCP sequence number validation in certain scenarios. Instead of rejecting out-of-range values, the systems accept a broad range of sequence numbers, potentially enabling attackers to manipulate TCP connections. While CISA has not assigned a CVE ID to this flaw at the time of publication, the advisory references a CSAF (Common Security Advisory Framework) document for further technical analysis:

• CSAF Advisory (JSON)

Impact Analysis

Successful exploitation of this vulnerability could allow remote attackers to:

• Disrupt TCP communications in industrial control systems (ICS).
• Execute denial-of-service (DoS) attacks by manipulating network traffic.
• Potentially gain unauthorized access to sensitive operational data if combined with other exploits.

The flaw affects multiple Siemens industrial products, though specific models and versions are not detailed in the advisory. Security teams should review the CSAF document for a complete list of impacted devices and mitigation guidance.

Recommendations

CISA and Siemens urge organizations to:

1. Review the CSAF advisory for a full list of affected products and technical specifics.
2. Apply vendor-supplied patches or mitigations as soon as they become available.
3. Monitor network traffic for anomalous TCP sequence patterns indicative of exploitation attempts.
4. Implement network segmentation to limit exposure of vulnerable devices.
5. Restrict remote access to industrial systems unless strictly necessary.

For further updates, refer to the original CISA advisory.