Several Zyxel firewall and WLAN controller products contain hardcoded credentials for an undocumented user account that has admin privileges.
Identified by EYE security researcher Niels Teusink, the vulnerability exists because the password for the “zyfwp” user account was stored in plaintext and was visible in one of the binaries on the system.
The account was designed for the delivery of automatic firmware updates through FTP and is present on Zyxel USG, ATP, VPN, ZyWALL, and USG FLEX devices.
While doing research on his personal Zyxel firewall, the security researcher discovered not only that the problematic user account exists with hardcoded credentials, but also that the account works both on SSH and the web interface.
The account, which has admin privileges, is not visible on the interface, and the device owner cannot change the password for it. The vulnerability is tracked as CVE-2020-29583.
In earlier firmware versions, the account did not have a password, with the security bug seemingly introduced in the latest firmware iteration. However, other vulnerabilities were found to impact previous firmware releases.
The security researcher notes that over 100.000 Zyxel USG/ATP/VPN devices worldwide appear to have their web interface exposed to the Internet. However, not all devices are running a vulnerable firmware version.
Because the zyfwp user account has admin privileges, exploitation could lead to compromised “confidentiality, integrity and availability of the device,” the researcher says. An attacker could change firewall settings, intercept traffic, or create VPN accounts to gain access to the local network.
Zyxel says the vulnerability impacts its ATP, USG, USG FLEX, and VPN series firewalls that are running firmware ZLD V4.60, as well as NXC2500 and NXC5500 AP controllers that are running firmware V6.00 through V6.10.
The company released ZLD V4.60 Patch1 firmware updates to address the vulnerability for the affected firewall products, and plans on releasing V6.10 Patch1 on January 8 for the vulnerable controllers.
Users are advised to update their devices as soon as possible, to ensure they are protected from the hardcoded credentials bug and from previously identified security flaws in these products.
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