An issue was discovered on Moxa AWK-3121 1.14 devices. It provides functionality so that an administrator can run scripts on the device to troubleshoot any issues. However, the same functionality allows an attacker to execute commands on the device. The POST parameter "iw_serverip" is susceptible to buffer overflow. By crafting a packet that contains a string of 480 characters, it is possible for an attacker to execute the attack.
https://seclists.org/bugtraq/2019/Jun/8
https://github.com/samuelhuntley/Moxa_AWK_1121/blob/master/Moxa_AWK_1121