Hello! @Zack_S
You can but you will need a file url (temporary or permanent). If you have the file buffer your best bet is a service that you can upload the binary to and get back a url that you can then update the Airtable attachment field with.
For example you could use AWS, upload the binary to S3 and then use the url to your S3 file for the Airtable attachement.
I also came across this while checking out make integrations: https://www.make.com/en/integrations/onesaas
I would do some research to make sure it's legit but they have an "Upload a Buffer File to a Temporary URL" integration which would also work here. Best of luck, hope it points you in the right direction!