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             AUSCERT External Security Bulletin Redistribution

                               ESB-2015.1913
Advisory (ICSA-15-202-01) Siemens SIPROTEC Denial-of-Service Vulnerability
                               22 July 2015

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Siemens SIPROTEC
Publisher:         US-CERT
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-5374  

Original Bulletin: 
   https://ics-cert.us-cert.gov/advisories/ICSA-15-202-01

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Advisory (ICSA-15-202-01)

Siemens SIPROTEC Denial-of-Service Vulnerability

Original release date: July 21, 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

Siemens has identified a denial-of-service vulnerability in the SIPROTEC 4 and
SIPROTEC Compact devices. This vulnerability was reported directly to Siemens
by Victor Nikitin from iGrids LLC Russia. Siemens has produced a new firmware
update to mitigate this vulnerability.

This vulnerability could be exploited remotely.

AFFECTED PRODUCTS

Siemens reports that the vulnerability affects the following versions:

    SIPROTEC 4 and SIPROTEC Compact product families

    All devices that include the EN100 Ethernet module version V4.24 or prior.

IMPACT

An attacker could remotely cause a denial of service by exploiting this 
vulnerability.

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 products, SIPROTEC 4 and SIPROTEC Compact devices, provide a wide
range of integrated protection, control, measurement, and automation functions
for electrical substations and other fields of application. The EN100 module 
is used for enabling IEC 61850 communications with electrical/optical 100 Mbit
interface for SIPROTEC 4 and SIPROTEC Compact devices. According to Siemens, 
SIPROTEC devices are deployed across several sectors including Energy. Siemens
estimates that these products are used worldwide.

VULNERABILITY CHARACTERIZATION

VULNERABILITY OVERVIEW

DENIAL OF SERVICE [a]

Specially crafted packets sent to Port 50000/UDP could cause a denial of 
service of the affected device. A manual reboot is required to return the 
device to service.

CVE-2015-5374 [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

An attacker with a low skill would be able to exploit this vulnerability.

MITIGATION

Siemens has provided firmware update V4.25 for the EN100 module to fix the 
vulnerability.

The firmware update for SIPROTEC 4 can be obtained here:

http://www.siemens.com/downloads/siprotec-4

The firmware update for SIPROTEC Compact can be obtained here:

http://www.siemens.com/downloads/siprotec-compact

For more information on this vulnerability and more detailed mitigation 
instructions, please see Siemens Security Advisory SSA-732541 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:

Configure firewall rules to appropriately restrict traffic to affected 
devices on Port 50000/UDP.

Monitor traffic to affected devices on Port 50000/UDP with an intrusion 
detection system (IDS).

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 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.

Additional mitigation guidance and recommended practices are publicly 
available in the ICSCERT 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.

a. CWE-400: Uncontrolled Resource Consumption ('Resource Exhaustion'), 
http://cwe.mitre.org/data/definitions/400.html, web site last accessed July 
21, 2015.

b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-5374, 
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 July 21, 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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