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AUSCERT External Security Bulletin Redistribution
ESB-2019.3106
Advisory (icsa-19-225-03) Siemens SCALANCE X Switches
14 August 2019
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AusCERT Security Bulletin Summary
---------------------------------
Product: Siemens SCALANCE X Switches
Publisher: ICS-CERT
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Mitigation
CVE Names: CVE-2019-10942
Original Bulletin:
https://www.us-cert.gov/ics/advisories/icsa-19-225-03
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ICS Advisory (ICSA-19-225-03)
Siemens SCALANCE X Switches
Original release date: August 13, 2019
Legal Notice
All information products included in http://ics-cert.us-cert.gov are
provided"as is" for informational purposes only. The Department of Homeland
Security (DHS) does not provide any warranties of any kind regarding any
information contained within. DHS does not endorse any commercial product or
service, referenced in this product or otherwise. Further dissemination of this
product is governed by the Traffic Light Protocol (TLP) marking in the header.
For more information about TLP, see http://www.us-cert.gov/tlp/ .
1. EXECUTIVE SUMMARY
o CVSS v3 8.6
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Siemens
o Equipment: SCALANCE X switches
o Vulnerability: Uncontrolled Resource Consumption
2. RISK EVALUATION
Successful exploitation of this vulnerability could cause a denial-of-service
condition.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following versions of SCALANCE X switches are affected:
o SCALANCE X-200: All versions
o SCALANCE X-200IRT: All versions
o SCALANCE X-200RNA: All versions
3.2 VULNERABILITY OVERVIEW
3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400
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 ).
3.3 BACKGROUND
o CRITICAL INFRASTRUCTURE SECTORS: Chemical, Critical Manufacturing, Energy,
Food and Agriculture, and Water and Wastewater Systems
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Germany
3.4 RESEARCHER
Younes Dragoni from Nozomi Networks reported this vulnerability to Siemens.
4. MITIGATIONS
Siemens has identified the following specific workarounds and mitigations users
can apply to reduce the risk:
o Disable telnet service on affected devices. Users should use SSH instead.
o Restrict network access to Port 23/TCP of the device.
Siemens recommends users configure their environment according to Siemens'
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 at the following
location:
http://www.siemens.com/cert/advisories
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 us-cert.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 us-cert.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted 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.
o Minimize network exposure for all control system devices and/or systems,
and ensure that they are not accessible from the Internet .
o Locate control system networks and remote devices behind firewalls, and
isolate them from the business network.
o When remote access is required, use secure methods, such as Virtual Private
Networks (VPNs), recognizing that VPNs may have vulnerabilities and should
be updated to the most current version available. Also recognize that VPN
is 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 onus-cert.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 us-cert.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted 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.
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