Vulnerabilities

Zyxel Devices Can Be Hacked via DNS Requests, Hardcoded Credentials

Multiple security vulnerabilities have been discovered by SEC Consult in various Zyxel devices, including flaws that involve sending unauthenticated DNS requests and hardcoded FTP credentials.

Ionut Arghire

September 3, 2019

Multiple security vulnerabilities have been discovered by SEC Consult in various Zyxel devices, including flaws that involve sending unauthenticated DNS requests and hardcoded FTP credentials.

The first issue impacts Zyxel security and networking devices from the USG, UAG, ATP, VPN and NXC products, which are prone to unauthenticated DNS requests, a SEC Consult advisory reads.

The security bug could allow unauthenticated users to check whether a domain is present or not via the web login interface. The IP address is embedded in the response if the host with the corresponding domain is present.

“A DNS request can be made by an unauthenticated attacker to either spam a DNS service of a third party with requests that have a spoofed origin or probe whether domain names are present on the internal network behind the firewall,” the advisory reads.

SEC Consult also discovered that hardcoded FTP credentials are present in multiple Zyxel Wi-Fi access points from the NWA, NAP and WAC series.

With these credentials at hand, an attacker could log on to the APs FTP server and fetch the configuration file that includes SSIDs and passwords, which would allow them to move to protected networks.

“An FTP service runs on the Zyxel wireless access point that contains the configuration file for the WiFi network. This FTP server can be accessed with hardcoded credentials that are embedded in the firmware of the AP. When the WiFi network is bound to another VLAN, an attacker can cross the network by fetching the credentials from the FTP server,” SEC Consult notes.

SEC Consult said it discovered the vulnerabilities in June and reported them to Zyxel at the end of the month. Hotfixes and firmware updates were released at the end of August. For some of the impacted devices, the vendor only released hotfixes, with firmware updates scheduled to be released in the coming months.

Zyxel customers are advised to install the patches and firmware updates for their devices as soon as possible.

SEC Consult’s advisories also include lists with all of the devices impacted by these vulnerabilities.

Written By Ionut Arghire

Ionut Arghire is an international correspondent for SecurityWeek.

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