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AUSCERT External Security Bulletin Redistribution
ESB-2016.2987
Siemens S7-300/400 PLC Vulnerabilities
15 December 2016
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AusCERT Security Bulletin Summary
---------------------------------
Product: Siemens S7-300/400 PLC
Publisher: ICS-CERT
Operating System: Network Appliance
Impact/Access: Access Privileged Data -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
Resolution: Mitigation
CVE Names: CVE-2016-9159 CVE-2016-9158
Original Bulletin:
https://ics-cert.us-cert.gov/advisories/ICSA-16-348-05
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Advisory (ICSA-16-348-05)
Siemens S7-300/400 PLC Vulnerabilities
Original release date: December 13, 2016
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/.
OVERVIEW
Zhu WenZhe from Beijing Acorn Network Technology has identified password
leak and denial-of-service vulnerabilities in Siemens' S7-300 and S7-400
programmable logic controllers. Siemens has released Security Advisory
SSA-731239 with advice to mitigate these vulnerabilities.
These vulnerabilities could be exploited remotely.
AFFECTED PRODUCTS
Siemens reports that the vulnerabilities affect the following versions of
SIMATIC PLC family:
SIMATIC S7-300 CPU family: All versions.
SIMATIC S7-400 CPU family: All versions.
IMPACT
Successful exploitation of these vulnerabilities could lead to a
denial-of-service condition or result in credential disclosure.
Impact to individual organizations depends on many factors that are unique
to each organization. NCCIC/ICS-CERT recommends that organizations evaluate
the impact of
these vulnerabilities based on their operational environment, architecture,
and product implementation.
BACKGROUND
Siemens is a multinational company headquartered in Munich, Germany.
The affected products, SIMATIC S7-300 and S7-400 PLC family, have been
designed for process control in industrial environments. According to
Siemens, SIMATIC S7-300 and S7-400 PLCs are deployed across several sectors
including Chemical, Energy, Food and Agriculture, and Water and Wastewater
Systems. Siemens estimates that these products are used worldwide.
VULNERABILITY CHARACTERIZATION
VULNERABILITY OVERVIEW
INADEQUATE ENCRYPTION STRENGTH[a]
An attacker with network access to Port 102/TCP (ISO-TSAP) could obtain
credentials from the PLC if Protection-level 2 is configured on the affected
devices. This vulnerability affects all listed affected products.
CVE-2016-9159[b] has been assigned to this vulnerability. A CVSS v3
base score of 7.5 has been calculated with a CVSS vector string of:
(AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).[c]
PROTECTION MECHANISM FAILURE[d]
Specially crafted packets sent to Port 80/TCP could cause the affected
devices to go into defect mode. A cold restart is required to recover the
system. This vulnerability affects all SIMATIC S7-300 PN CPUs, and all
SIMATIC S7-400 PN V6 and V7 CPUs.
CVE-2016-9158[e] has been assigned to this vulnerability. A CVSS v3
base score of 7.5 has been calculated with a CVSS vector string of:
(AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).[f]
VULNERABILITY DETAILS
EXPLOITABILITY
These vulnerabilities could be exploited remotely.
EXISTENCE OF EXPLOIT
No known public exploits specifically target these vulnerabilities.
DIFFICULTY
An attacker with a low skill would be able to exploit these vulnerabilities.
MITIGATION
Siemens recommends the following mitigations:
Deactivate the web server.
Apply Protection-level 3 read/write protection.
Apply cell protection concept.
Apply defense-in-depth strategies.
Use VPN for protecting network communication between cells.
Siemens strongly recommends users protect network access with appropriate
mechanisms (e.g., firewalls, segmentation, VPN). Siemens also advises
that users configure the operational environment according to Siemens'
Operational Guidelines for Industrial Security:
https://www.siemens.com/cert/operational-guidelines-industrial-security
For more information on this vulnerability and more detailed mitigation
instructions, please see Siemens Security Advisory SSA-731239 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 these vulnerabilities. Specifically, users should:
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.
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.
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. 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.
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.
a.
CWE- 326: Inadequate Encryption Strength,
https://cwe.mitre.org/data/definitions/326.html, web site last accessed
December 13, 2016.
b.
NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-9159,
NIST uses this advisory to create the CVE web site report. This web
site will be active sometime after publication of this advisory.
c.
CVSS Calculator,
http://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:...,
web site last accessed December 13, 2016.
d.
CWE-693: Protection Mechanism Failure,
https://cwe.mitre.org/data/definitions/693.html, web site last accessed
December 13, 2016.
e.
NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-9158,
NIST uses this advisory to create the CVE web site report. This web
site will be active sometime after publication of this advisory.
f.
CVSS Calculator,
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S...,
web site last accessed December 13, 2016.
Contact Information
For any questions related to this report, please contact ICS-CERT at:
Email: ics-cert@hq.dhs.gov
Toll Free: 1-877-776-7585
International Callers: (208) 526-0900
For industrial control systems security information and incident reporting:
http://ics-cert.us-cert.gov
ICS-CERT continuously strives to improve its products and services. You
can help by choosing one of the links below to provide feedback about
this product.
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