ZyXEL ZyWALL 1050 has a hard-coded password for the Quagga and Zebra processes that is not changed when it is set by a user, which allows remote attackers to gain privileges.
packetstormsecurity.org/0803-exploits/ZyWALL.pdf
secunia.com/advisories/29237
www.secumania.org/exploits/remote/zyxel-zywall-quagga_zebra-%28default-pass%29-remote-root-vulnerability-2008032143791/
www.securityfocus.com/bid/28184
www.vupen.com/english/advisories/2008/0990/references
exchange.xforce.ibmcloud.com/vulnerabilities/41424
www.exploit-db.com/exploits/5289