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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-19-281-03) Siemens SIMATIC WinAC RTX (F) 2010
9 October 2019
AusCERT Security Bulletin Summary
Product: Siemens SIMATIC WinAC RTX (F) 2010
Operating System: Windows
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2019-13921
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ICS Advisory (ICSA-19-281-03)
Siemens SIMATIC WinAC RTX (F) 2010
Original release date: October 08, 2019
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1. EXECUTIVE SUMMARY
o CVSS v3 7.5
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Siemens
o Equipment: SIMATIC WinAC RTX (F) 2010
o Vulnerability: Uncontrolled Resource Consumption
2. RISK EVALUATION
Successful exploitation of this vulnerability could allow an attacker to
perform a denial-of-service attack that could compromise the availability of
the service provided by the software.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following versions of Siemens SIMATIC WinAC RTX (F) 2010, software
controller for PC-based automation solutions, are affected:
o SIMATIC WinAC RTX (F) 2010 all versions
3.2 VULNERABILITY OVERVIEW
3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400
An unauthenticated attacker sending a large HTTP request to the host where
WinAC RTX is running may trigger a denial-of-service condition.
CVE-2019-13921 has been assigned to this vulnerability. A CVSS v3 base score of
7.5 has been assigned; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/C:N/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Germany
Tal Keren from Claroty reported this vulnerability to Siemens.
Siemens has identified the following specific workarounds and mitigations users
can apply to reduce the risk:
o Restrict network access to the host containing the affected service.
o If the service is not used as a server, configure Windows Firewall to
disable communications on the port of the vulnerable service.
As a general security measure, Siemens strongly recommends protecting network
access to devices with appropriate mechanisms. In order to operate the devices
in a protected IT environment, Siemens recommends configuring the environment
according to Siemens' operational guidelines for Industrial Security , and
following the recommendations in the product manuals.
Additional information on Industrial Security by Siemens can be found at:
For more information on this vulnerability and more detailed mitigation
instructions, please see Siemens security advisory SSA-878278 at the following
CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:
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 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
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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