ESB-2018.0995 - [Appliance] WAGO 750 Series: Denial of service - Remote/unauthenticated 2018-04-04

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.0995
                 Advisory (ICSA-18-088-01) WAGO 750 Series
                               4 April 2018

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        AusCERT Security Bulletin Summary
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Product:           WAGO 750 Series
Publisher:         ICS-CERT
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-8836  

Original Bulletin: 
   https://ics-cert.us-cert.gov/advisories/ICSA-18-088-01

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Advisory (ICSA-18-088-01) WAGO 750 Series

Original release date: March 29, 2018

Legal Notice

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"as is" for informational purposes only. The Department of Homeland Security 
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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/.

CVSS v3 5.3

ATTENTION: Exploitable remotely/low skill level to exploit.

Vendor: WAGO

Equipment: 750 Series

Vulnerability: Improper Resource Shutdown or Release

AFFECTED PRODUCTS

The following versions of 750 series PLC are affected:

    750-880 firmware version 10 and prior,
    750-881 firmware version 10 and prior,
    750-852 firmware version 10 and prior,
    750-882 firmware version 10 and prior,
    750-885 firmware version 10 and prior,
    750-831 firmware version 10 and prior,
    750-889 firmware version 10 and prior, and
    750-829 firmware version 10 and prior.

IMPACT

Successful exploitation of this vulnerability could allow a denial-of-service
condition affecting the ability of the device to establish connections to 
commissioning and service software tools.

MITIGATION

WAGO has released new firmware addressing this vulnerability that can be 
obtained by contacting WAGO support via email at support@wago.com (link sends
e-mail).

If updating the firmware is not feasible WAGO recommends that users disable 
the WAGO Service Communication via WBM or limit the access to Ports 6626 and 
2455/TCP/IP to trusted devices.

For more information see WAGOs security advisory:

Vulnerability-in-the-WAGO-Ethernet-TCP-IP-driver.pdf (link is external)

NCCIC recommends users take defensive measures to minimize the risk of 
exploitation of this vulnerability. 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.

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 in the NCCIC 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 NCCIC for 
tracking and correlation against other incidents.

No known public exploits specifically target this vulnerability.

VULNERABILITY OVERVIEW

IMPROPER RESOURCE SHUTDOWN OR RELEASE CWE-404

A remote attack may take advantage of an improper implementation of the 3 way
handshake during a TCP connection affecting the communications with commission
and service tools. Specially crafted packets may also be sent to Port 
2455/TCP/IP, used in Codesys management software, which may result in a 
denial-of-service condition of communications with commissioning and service 
tools.

CVE-2018-8836 has been assigned to this vulnerability. A CVSS v3 base score of
5.3 has been assigned; the CVSS vector string is 
(AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

RESEARCHER

Younes Dragoni of Nozomi Networks reported the vulnerability to NCCIC.

BACKGROUND

Critical Infrastructure Sectors: Commercial Facilities, Critical 
Manufacturing, Energy, and Transportation Systems

Countries/Areas Deployed: Worldwide

Company Headquarters Location: United States, Germany, Switzerland, Poland, 
China, and India

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