If the Cuban passport holders want to apply visa at Vietnam Embassy, they should to know that:
Visa administrative Institution: Vietnam Embassy
Processing time: depends on you how fast you need. But for sure, you should make a call to Vietnam Embassy for details.
Required Documents: passport, money and 1 new envelope with stamp on it and your exact home address in order to avoid losing issues.
How to apply: please take a look at contact information of Vietnam Embassy below
EMBASSY OF VIETNAM IN LA HABANA, CUBA
Address: # 1802, 5ta. Avenide, Esquina A 18, Miramarm Playa. La Habana, CUBA
Phone: (537) 204 1502
Fax: (537) 204 1041
Email: firstname.lastname@example.org | email@example.com