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AUSCERT External Security Bulletin Redistribution
Advisory (ICSA-17-131-01) Phoenix Contact GmbH mGuard
12 May 2017
AusCERT Security Bulletin Summary
Product: Phoenix Contact GmbH mGuard
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Unauthorised Access -- Remote/Unauthenticated
CVE Names: CVE-2017-7937 CVE-2017-7935
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Phoenix Contact GmbH mGuard
Original release date: May 11, 2017
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CVSS v3 8.6
ATTENTION: Remotely exploitable/low skill level to exploit
Vendor: Phoenix Contact GmbH
Vulnerabilities: Resource Exhaustion, Improper Authentication
The following versions of mGuard, a network device, are affected:
mGuard firmware versions 8.3.0 to 8.4.2
Successful exploitation of these vulnerabilities could allow an attacker to
disrupt the availability of the device and gain unauthorized access to the
Phoenix Contact GmbH recommends that users upgrade to firmware Version 8.5.0,
or higher, to mitigate the vulnerabilities.
NCCIC/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 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.
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.
No known public exploits specifically target these vulnerabilities.
RESOURCE EXHAUSTION CWE-400
An attacker may compromise the devices availability by performing multiple
initial VPN requests.
CVE-2017-7935 has been assigned to this vulnerability. A CVSS v3 base score of
8.6 has been assigned; the CVSS vector string is
IMPROPER AUTHENTICATION CWE-287
An attacker may be able to gain unauthorized access to the user firewall when
RADIUS servers are unreachable.
CVE-2017-7937 has been assigned to this vulnerability. A CVSS v3 base score of
4.0 has been assigned; the CVSS vector string is
Phoenix Contact GmbH self-reported these vulnerabilities.
Critical Infrastructure Sector: Critical Manufacturing
Countries/Areas Deployed: Worldwide
Company Headquarters Location: Germany
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