Solved
Hi @민우한1
since this is your organization's domain, Adobe cannot really do anything about it.
Reach out to your system administrators how the CNAME can be unregistered.
On top of that, since Adobe is typically providing the certificate for this subdomain, you should contact support once the CNAME entry is removed from your organization side.
Enter your E-mail address. We'll send you an e-mail with instructions to reset your password.