Some of the vulnerabilities discovered recently by Google researchers in the Dnsmasq network services software affect several Siemens SCALANCE industrial communications products.
Dnsmasq is a lightweight tool designed to provide DNS, DHCP, router advertisement and network boot services for small networks. It can be found in Linux distributions, smartphones, routers, and many Internet of Things (IoT) devices.
Google’s security team recently found that the tool is affected by seven flaws, including ones that can be exploited via DNS or DHCP for remote code execution, information disclosure, and denial-of-service (DoS) attacks. Linux distributions, Amazon, Cisco, Synology, Sophos and other companies warned customers about the potential risks shortly after the issues were disclosed in early October.
Earlier this month, Siemens also published an advisory to inform customers that four of the seven vulnerabilities affect some of its SCALANCE products, including W1750D controller-based direct access points, M800 industrial routers, and S615 firewalls.
Three of the flaws affecting Siemens devices, CVE-2017-13704, CVE-2017-14495 and CVE-2017-14496, can be exploited to crash the Dnsmasq process by sending specially crafted requests to the service on UDP port 53.
The SCALANCE products are also impacted by CVE-2017-14491, one of the most serious vulnerabilities discovered by Google researchers in Dnsmasq. This security hole allows an attacker to cause a DoS condition or possibly execute arbitrary code.
“In order to exploit this vulnerability, an attacker must be able to trigger DNS requests from the device, and must be in a position that allows him to inject malicious DNS responses, e.g. the attacker must be in a Man-in-the-Middle position,” Siemens said.
The company says it’s preparing patches for the vulnerable products. In the meantime, it has advised customers to apply defense-in-depth recommendations, deploy firewall rules to block incoming traffic on UDP port 53 (applies to W1750D if OpenDNS, Captive
Portal or URL redirection functionality is not used), and disable the DNS proxy and configure devices to use a different DNS server (applies to M800 and S615).
Siemens has also reported the vulnerabilities to ICS-CERT, which also published an advisory this week.