Original Article Summary

View CSAF 1. EXECUTIVE SUMMARY CVSS v3 8.8 ATTENTION: Exploitable remotely/low attack complexity Vendor: Festo SE & Co. KG Equipment: MSE6-C2M/D2M/E2M Vulnerability: Hidden Functionality 2. RISK EVALUATION Successful exploitation of this vulnerability could lead to a complete loss of confidentiality, integrity, and availability. 3. TECHNICAL DETAILS 3.1 AFFECTED PRODUCTS Festo reports the following products are affected: MSE6-C2M-5000-FB36-D-M-RG-BAR-M12L4-AGD: All versions MSE6-C2M-5000-FB36-D-M-RG-BAR-M12L5-AGD: All versions MSE6-C2M-5000-FB43-D-M-RG-BAR-M12L4-MQ1-AGD: All versions MSE6-C2M-5000-FB43-D-M-RG-BAR-M12L5-MQ1-AGD: All versions MSE6-C2M-5000-FB44-D-M-RG-BAR-AMI-AGD: All versions MSE6-C2M-5000-FB44-D-RG-BAR-AMI-AGD: All versions MSE6-D2M-5000-CBUS-S-RG-BAR-VCB-AGD: All versions MSE6-E2M-5000-FB13-AGD: All versions MSE6-E2M-5000-FB36-AGD: All versions MSE6-E2M-5000-FB37-AGD: All versions MSE6-E2M-5000-FB43-AGD: All versions MSE6-E2M-5000-FB44-AGD: All versions 3.2 VULNERABILITY OVERVIEW 3.2.1 Hidden Functionality CWE-912 In Festo MSE6 product-family, a remote authenticated, low-privileged attacker could use functions of undocumented test mode, which could lead to a complete loss of confidentiality, integrity, and availability. CVE-2023-3634 has been assigned to this vulnerability. A CVSS v3.1 base score of 8.8 has been calculated; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). 3.3 BACKGROUND CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing COUNTRIES/AREAS DEPLOYED: Worldwide COMPANY HEADQUARTERS LOCATION: Germany 3.4 RESEARCHER Festo coordinated this vulnerability with CERT@VDE. 4. MITIGATIONS Festo has updated the user documentation in the next product version to address this issue. For more information, see the associated Festo SE & Co. KG security advisory FSA-202304 FSA-202304: Festo: MSE6-C2M/D2M/E2M Incomplete User Documentation of Remote Accessible Functions - HTML, FSA-202304: Festo: MSE6-C2M/D2M/E2M Incomplete User Documentation of Remote Accessible Functions - CSAF. CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as: Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolating them from business networks. When remote access is required, use more secure methods, such as virtual private networks (VPNs). Recognize VPNs may have vulnerabilities, should be updated to the most recent version available, and are only as secure as the connected devices. 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. CISA also recommends users take the following measures to protect themselves from social engineering attacks: Do not click web links or open attachments in unsolicited email messages. Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams. Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks. No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time. 5. UPDATE HISTORY November 20, 2025: Initial Republication of Festo FSA-202304