Security flaws in a widely used DNS software package could allow attackers to send users to malicious websites or to remotely hijack their devices

Millions of devices could be vulnerable to Domain Name System (DNS) cache poisoning and remote code execution attacks due to seven security flaws in dnsmasq, DNS forwarding and caching software commonly found in smartphones, desktops, servers, routers and other Internet of Things devices, according to Israel-based security company JSOF, which discovered the security holes.

Collectively dubbed DNSpooq, the vulnerabilities in the open-source utility affect a variety of devices and firmware, including those made by some of the world’s leading tech companies.

“Some of the DNSpooq vulnerabilities allow for DNS cache poisoning and one of the DNSpooq vulnerabilities could permit a potential Remote Code execution that could allow a takeover of many brands of home routers and other networking equipment, with millions of devices affected, and over a million instances directly exposed to the Internet,” warned JSOF. According to Shodan, there are almost 1.2 million dnsmasq servers exposed to the internet, with yet more vulnerable devices confined to internal networks but also at risk.

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Researchers identified no fewer than 40 vendors that use dnsmasq in a wide range of products and in various pieces of firmware and software. The list includes big names such as Cisco, Asus AT&T, Comcast, Siemens, Dell, Linksys, Qualcomm, Motorola, and IBM, just to mention but a few. Whether and to what extent devices are affected depends on how they use dnsmasq. 

DNSpooq consists of seven vulnerabilities divided into two groups – three that could allow DNS cache poisoning attacks and four buffer overflow vulnerabilities, one of which could lead to remote code execution and device takeover.

An overview of the DNSpooq vulnerabilities (source: JSOF)

“The impact of DNS cache poisoning of the routing equipment DNS forwarding server can potentially lead to different kinds of fraud if users believe they are browsing to one website but are actually routed to another,” the researchers said. They went on to add that each device susceptible to DNS cache poisoning might also be taken over by an attacker.

While on their own the security bugs present a limited risk, once chained and combined they could also be used to conduct Distributed Denial-of-Service (DDoS) attacks as well as wormable attacks that could spread malware between devices and networks.

Researchers disclosed the vulnerabilities in August 2020 and went public with their discovery after the embargo ended this month. While highlighting a number of workarounds in its technical whitepaper to DNSpooq, JSOF advised everybody to apply the best “antidote” – update to dnsmasq version 2.83. In the meantime, multiple vendors have released their respective advisories, mitigations, workarounds and patches, which are now neatly listed on the website of the CERT Coordination Center at Carnegie Mellon University. The Cybersecurity and Infrastructure Security Agency (CISA) also had some advice to share for organizations that use vulnerable products.

In June 2020, JSOF discovered and disclosed 19 security vulnerabilities that were collectively dubbed Ripple20 and were found to affect a popular TCP/IP software library used by millions of connected devices.