Rating:

It is a DNS server that serves an RSA publickey TXT record, and responds to command output when queried with an RSA-OAEP encrypted command.

Since I couldn't find any tool that allowed me to send malformed DNS messages, glued something together that send the command and read back the output.

Original writeup (https://www.nevi.dev/2022/03/14/writeup-utctf-2022/#malformed-query-networking).