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AUSCERT External Security Bulletin Redistribution
ESB-2015.2535
Mitsubishi Electric MELSEC FX-Series Controllers Denial of Service
1 October 2015
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AusCERT Security Bulletin Summary
---------------------------------
Product: Mitsubishi Electric MELSEC FX-Series Controllers
Publisher: ICS-CERT
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2015-3938
Original Bulletin:
https://ics-cert.us-cert.gov/advisories/ICSA-15-146-01
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Advisory (ICSA-15-146-01)
Mitsubishi Electric MELSEC FX-Series Controllers Denial of Service
Original release date: September 29, 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
This advisory was originally posted to the US-CERT secure Portal library
on May 26, 2015, and is being released to the NCCIC/ICS-CERT web site.
Ralf Spenneberg of OpenSource Security has identified a denial of service
(DoS) vulnerability in the Mitsubishi Electric Automation, Inc., (Mitsubishi
Electric) MELSEC FX-series controllers. Mitsubishi Electric has produced
a new version that is not vulnerable to this issue.
This vulnerability could be exploited remotely.
AFFECTED PRODUCTS
The following MELSEC FX-series are affected:
MELSEC FX3G Series PLCs.
IMPACT
A machine requires rebooting after this vulnerability has been exploited.
Impact to individual organizations depends on many factors that are unique
to each organization. ICS-CERT recommends that organizations evaluate
the impact of this vulnerability based on their operational environment,
architecture, and product implementation.
BACKGROUND
Mitsubishi Electric is based in Vernon Hills, Illinois.
The affected products, MELSEC FX-series, are programmable logic
controllers. According to Mitsubishi Electric, MELSEC FX-series controllers
are deployed across several sectors including Commercial Facilities, Critical
Manufacturing, Energy, Water and Wastewater Systems, and others. Mitsubishi
Electric estimates that these products are used primarily in Asia with a
small percentage in the United States and Europe.
VULNERABILITY CHARACTERIZATION
VULNERABILITY OVERVIEW
IMPROPER HANDLING OF PARAMETERS[a]
The built-in HTTP application is unable to handle parameters that are
longer than expected. A long parameter can cause a denial of service
condition that requires a reboot to recover.
CVE-2015-3938[b] has been assigned to this vulnerability. A CVSS
v2 base score of 7.1 has been assigned; the CVSS vector string is
(AV:N/AC:M/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
An attacker with a medium skill would be able to exploit this vulnerability.
MITIGATION
Mitsubishi Electric enhanced the MELSEC FX PLCs to prevent the DoS from
occurring in new products starting in April 2015. They cannot guarantee
the quality of new firmware in old hardware, so they do not plan to issue
a firmware upgrade to existing customers.
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.
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 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
(www.ics-cert.org).
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-233: Improper Handling of Parameters,
http://cwe.mitre.org/data/definitions/233.html, web site last accessed
May 26, 2015.
b.
NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-3938,
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:M/Au:N/C:N/I:N/A:C
, web site last accessed May 26, 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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The University of Queensland
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