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AUSCERT External Security Bulletin Redistribution
Advisory (ICSA-19-043-04) Siemens SIMATIC S7-300 CPU
13 February 2019
AusCERT Security Bulletin Summary
Product: Siemens SIMATIC S7-300 CPU
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2018-16561
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Siemens SIMATIC S7-300 CPU
Original release date: February 12, 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 S7-300 CPU
o Vulnerability : Improper Input Validation
2. RISK EVALUATION
Successful exploitation of this vulnerability could crash the device being
accessed, resulting in a denial-of-service condition.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Siemens reports the following SIMATIC S7-300 CPU product is affected:
o SIMATIC S7-300 CPUs: All versions prior to v3.X.16
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER INPUT VALIDATION CWE-20
The affected CPUs improperly validate S7 communication packets, which could
cause a denial-of-service condition of the CPU. The CPU will remain in DEFECT
mode until manual restart.
Successful exploitation requires an attacker to send a specially crafted S7
communication packet to a communication interface of the CPU. This includes
Ethernet, PROFIBUS, and Multi Point Interfaces (MPI). The vulnerability could
allow a denial-of-service condition of the core functionality of the CPU.
CVE-2018-16561 has been assigned to this vulnerability. A CVSS v3 base score of
7.5 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS : Chemical, Critical Manufacturing, Energy,
Food and Agriculture, Water and Wastewater Systems
o COUNTRIES/AREAS DEPLOYED : Worldwide
o COMPANY HEADQUARTERS LOCATION : Germany
China Industrial Control Systems Cyber Emergency Response Team (CIC) reported
this vulnerability to Siemens.
Siemens recommends users update to Version 3.X.16, which can be downloaded from
the following link:
Siemens has identified the following specific workarounds and mitigations users
can apply to reduce the risk:
o Siemens recommends operating the devices only within trusted networks
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 ( https://
www.siemens.com/cert/operational-guidelines-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 associated software updates,
please see Siemens security advisory SSA-306710 on their website:
NCCIC 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.
NCCIC reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.
NCCIC also provides a section for control systems security recommended
practices on the ICS-CERT web page. 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-CERT website 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 NCCIC for tracking
and correlation against other incidents.
No known public exploits specifically target this vulnerability.
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