As of January 10, 2023, CISA will no longer be updating ICS security advisories for Siemens product vulnerabilities beyond the initial advisory. For the most up-to-date information on vulnerabilities in this advisory, please see Siemens' ProductCERT Security Advisories (CERT Services | Services | Siemens Global). 
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1. EXECUTIVE SUMMARY
CVSS v4 8.7
ATTENTION: Exploitable remotely/low attack complexity
Vendor: Siemens
Equipment: SIMATIC CP 343-1, SIMATIC CP 343-1Lean, SIPLUS NET CP 343-1, SIPLUS NET CP 343-1 Lean
Vulnerability: Improper Verification of Source of a Communication Channel
2. RISK EVALUATION
Successful exploitation of this vulnerability could allow an unauthenticated remote attacker to create a denial-of-service condition by injecting spoofed TCP RST packets.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following Siemens products are affected:
SIMATIC CP 343-1 (6GK7343-1EX30-0XE0): All versions
SIMATIC CP 343-1 Lean (6GK7343-1CX10-0XE0): All versions
SIPLUS NET CP 343-1 (6AG1343-1EX30-7XE0): All versions
SIPLUS NET CP 343-1 Lean (6AG1343-1CX10-2XE0): All versions
3.2 Vulnerability Overview
3.2.1 IMPROPER VERIFICATION OF SOURCE OF A COMMUNICATION CHANNEL CWE-940
Affected products incorrectly validate TCP sequence numbers. This could allow an unauthenticated remote attacker to create a denial-of-service condition by injecting spoofed TCP RST packets.
CVE-2023-51440 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
A CVSS v4 score has also been calculated for CVE-2023-51440. A base score of 8.7 has been assigned; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N).
3.3 BACKGROUND
CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
COUNTRIES/AREAS DEPLOYED: Worldwide
COMPANY HEADQUARTERS LOCATION: Germany
3.4 RESEARCHER
Siemens reported this vulnerability to CISA.
4. MITIGATIONS
Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:
Apply network segmentation and defense-in-depth practices to reduce likelihood of a threat actor to be able to reach a potentially vulnerable device.
As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. To operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens' operational guidelines for industrial security and following recommendations in the product manuals.
Additional information on industrial security by Siemens can be found on the Siemens industrial security webpage.
For more information see the associated Siemens security advisory SSA-516818 in HTML and CSAF.
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.
No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.
5. UPDATE HISTORY
February 15, 2024: Initial Publication


https://www.cisa.gov/news-events/ics-advisories/icsa-24-046-04