How many blank pages must the passport have?
At least two blank pages.
In detail
The document requires at least two (2) blank pages. “Blank” means genuinely blank — a page carrying an old visa, an immigration stamp or an entry/exit mark does not count. Frequent travellers often have pages left but stamps on all of them, which does not satisfy the requirement. Open the passport and count them yourself before submitting. If you have run out, a new passport is the only route.