Siemens SCALANCE S613 Denial-of-Service Vulnerability

OVERVIEW

Siemens has identified a resource exhaustion vulnerability that causes a denial-of-service condition in the Siemens SCALANCE S613 device. Siemens recommends that customers contact Siemens customer support in order to obtain advice on a solution for the customer’s specific environment.

This vulnerability could be exploited remotely.

AFFECTED PRODUCTS

The following Siemens SCALANCE versions are affected:

• SCALANCE S613 (MLFB: 6GK5613-0BA00-2AA3): All versions.

IMPACT

An attacker exploiting this vulnerability can cause the device to enter a state that requires a manual reboot to recover.

Impact to individual organizations depends on many factors that are unique to each organization. NCCIC/ICS-CERT recommends that organizations evaluate the impact of this vulnerability based on their operational environment, architecture, and product implementation.

BACKGROUND

Siemens is a multinational company headquartered in Munich, Germany.

The affected product, Siemens SCALANCE firewall, is used to protect trusted industrial networks from untrusted networks. It allows filtering of incoming and outgoing network connections in different ways. According to Siemens, Siemens SCALANCE is deployed across several sectors including Chemical, Critical Manufacturing, Defense Industrial Base, Energy, Transportation Systems, and Water and Wastewater Systems. Siemens estimates that this product is used worldwide.

VULNERABILITY CHARACTERIZATION

VULNERABILITY OVERVIEW

Certain legitimate messages sent to Port 443/TCP could cause a denial-of-service condition affecting the integrated web server of affected devices. A manual reboot is required to recover the web server of the device.

CVE-2016-3963NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-3963, web site last accessed April 12, 2016. has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).CVSS Calculator, https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L, web site last accessed April 12, 2016.

VULNERABILITY DETAILS

EXPLOITABILITY

This vulnerability could be exploited remotely.

EXISTENCE OF EXPLOIT

No known public exploits specifically target this vulnerability.

DIFFICULTY

An attacker with a low skill would be able to exploit this vulnerability.

MITIGATION

Siemens recommends that customers contact Siemens Customer Support in order to obtain advice on a solution for the customer’s specific environment. Siemens support can be contacted via email at support.automation@siemens.com or via phone +49 (911) 895-7222.

For more information on this vulnerability and more detailed mitigation instructions, please see Siemens Security Advisory SSA-751155 at the following location:

http://www.siemens.com/cert/advisories

ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:

• Monitor traffic to Port 443/TCP.
• Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls, and isolate them from the business network.

ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page at: http://ics-cert.us-cert.gov/content/recommended-practices. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies, that is available for download from the ICS-CERT web site (http://ics-cert.us-cert.gov/).

Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.

• Siemens