This updated advisory is a follow-up to the advisory update titled ICSA-19-225-03 Siemens SCALANCE X Switches (Update C) that was published September 14, 2021, to the ICS webpage on www.cisa.gov/uscert.
Successful exploitation of this vulnerability could cause a denial-of-service condition.
The following versions of SCALANCE X switches are affected:
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An attacker may send large message packages repeatedly to the telnet service, which may allow a denial-of-service condition.
CVE-2019-10942 has been assigned to this vulnerability. A CVSS v3 base score of 8.6 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H).
Younes Dragoni and Alessandro Di Pinto from Nozomi Networks and Artem Zinenko from Kaspersky reported these vulnerability details to Siemens.
Siemens has identified the following specific updates, workarounds and mitigations users can apply to reduce the risk:
Siemens recommends users configure their environment according to Siemensβ operational guidelines for industrial security and follow the recommendations in the product manuals.
Additional information on industrial security by Siemens can be found at:
<https://www.siemens.com/industrialsecurity>
For more information on the vulnerability and more detailed mitigation instructions, please see Siemens security advisory SSA-100232
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:
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 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 on the ICS webpage on cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01BβTargeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to CISA for tracking and correlation against other incidents.
No known public exploits specifically target this vulnerability.
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2019-10942
www.siemens.com/cert/advisories
cert-portal.siemens.com/operational-guidelines-industrial-security.pdf
cwe.mitre.org/data/definitions/410.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
support.industry.siemens.com/cs/ww/en/view/109792534/
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