ServiceNow - Upload Jira attachment to Incident

Creata a Action

Do not select any template

Click Create

Enter POST as URL

Enter https://your_instance.service-now.com/api/now/attachment/upload

Select Latest as Issue Attachment(s) option

Add these form vars in the table

Save the action

To Test, simulate a case where the trigger send the iHub call or switch to All on Issue Attachmen(s) and click Test button and add an Issue.