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AUSCERT External Security Bulletin Redistribution
ESB-2015.0527
Siemens SIMATIC S7-300 CPU Denial-of-Service Vulnerability
6 March 2015
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AusCERT Security Bulletin Summary
---------------------------------
Product: Siemens SIMATIC S7-300 CPU Family
Publisher: US-CERT
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2015-2177
Original Bulletin:
https://ics-cert.us-cert.gov/advisories/ICSA-15-064-04
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Advisory (ICSA-15-064-04)
Siemens SIMATIC S7-300 CPU Denial-of-Service Vulnerability
Original release date: March 05, 2015
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
Johannes Klick, Christian Pfahl, Martin Gebert, and Lucas Jacob from Freie
Universitt Berlins work team SCADACS have identified a Denial-of-Service (DoS)
vulnerability in Siemens SIMATIC S7-300 CPUs. Siemens has developed
mitigations for this vulnerability.
This vulnerability could be exploited remotely.
AFFECTED PRODUCTS
The following SIMATIC S7-300 CPUs are affected:
SIMATIC S7-300 CPU family: all versions.
IMPACT
This vulnerability could allow attackers to perform a DoS attack over the
network without prior authentication against S7-300 CPUs under certain
conditions. A cold restart is required to recover the system.
Impact to individual organizations depends on many factors that are unique to
each organization. NCCIC/ICS-CERT recommends that organizations evaluate the
impact of this vulnerability based on their operational environment,
architecture, and product implementation.
BACKGROUND
Siemens is a multinational company headquartered in Munich, Germany.
The affected product, SIMATIC S7-300 CPU, have been designed for process
control in industrial environments. This product is deployed across several
sectors including Chemical, Energy, Food and Agriculture, and Water and
Wastewater Systems. Siemens estimates that these products are used primarily
in the United States and Europe with a small percentage in Asia.
VULNERABILITY CHARACTERIZATION
VULNERABILITY OVERVIEW
DENIAL-OF-SERVICE ATTACK[a]
Specially crafted packets sent to Port 102/TCP (ISO-TSAP) or via Profibus
could cause the affected device to go into defect mode. A cold restart is
required to recover the system.
CVE-2015-2177[b] has been assigned to this vulnerability. A CVSS v2 base score
of 7.8 has been assigned; the CVSS vector string is
(AV:N/AC:L/Au:N/C:N/I:N/A:C).[c]
VULNERABILITY DETAILS
EXPLOITABILITY
This vulnerability could be exploited remotely.
EXISTENCE OF EXPLOIT
No known public exploits specifically target this vulnerability.
DIFFICULTY
Crafting a working exploit for this vulnerability would be difficult.
MITIGATION
Siemens recommends the following mitigations:
Apply protection-level 3 (Read/Write protection),
Apply cell protection concept,[d]
Use VPN for protecting network communication between cells, and
Apply Defense-in-Depth.[e]
For more information on these vulnerabilities and detailed instructions,
please see Siemens Security Advisory SSA-987029 at the following location:
http://www.siemens.com/cert/advisories
ICS-CERT encourages asset owners to take additional defensive measures to
protect against this and other cybersecurity risks.
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.
ICS-CERT also provides a section for control systems security recommended
practices on the ICS-CERT web page at:
http://ics-cert.us-cert.gov/content/recommended-practices. Several recommended
practices are available for reading and download, including Improving
Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
ICS-CERT reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.
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
(http://ics-cert.us-cert.gov/).
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.
In addition, ICS-CERT recommends that users take the following measures to
protect themselves from social engineering attacks:
Do not click web links or open unsolicited attachments in email messages.
Refer to Recognizing and Avoiding Email Scams[f] for more information on
avoiding email scams.
Refer to Avoiding Social Engineering and Phishing Attacks[g] for more
information on social engineering attacks.
a. CWE-404: Improper Resource Shutdown or Release,
http://cwe.mitre.org/data/definitions/404, web site last accessed March 05,
2015.
b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-2177, 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://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:N/I:N/A:C, web
site last accessed March 05, 2015.
d. Operational Guidelines for Industrial Security,
https://www.siemens.com/cert/operational-guidelines-industrial-security, web
site last accessed March 05, 2015.
e. Further information about Defense-in-Depth,
http://www.industry.siemens.com/topics/global/en/industrial-security/con...,
web site last accessed March 05, 2015.
f. Recognizing and Avoiding Email Scams,
http://www.us-cert.gov/reading_room/emailscams_0905.pdf, web site last
accessed March 05, 2015.
g. National Cyber Alert System Cyber Security Tip ST04-014,
http://www.us-cert.gov/cas/tips/ST04-014.html, web site last accessed March
05, 2015.
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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