As per the specification the CDC interface need the data endpoints as Bulk endpoint only. The bulk endpoint has limitation on the packet size of 64 bytes as per the USB Full speed specification.
The CDC data can be accessed using API(OUT packet).
You have to receive data in chunks of 64 bytes (like by polling) and process accordingly.
Please check this KBA when you try to send 64 bytes/Maximum Payload Size Packet in USBUART componenet:
These links may be useful:
thank you for your advice.