Nether Fortresses can generate without a lava room and corridor section.

The Bug

Nether Fortresses generate with exactly one 'lava room' (a room with a single source of lava in the middle), and then branch off into two sections, an unroofed bridge section with blaze spawners, and a roofed corridor section with chests and sometimes nether wart.

I found this nether fortress that is only the bridge section.

Seed: 7443427916387145916

/execute in the_nether run tp @s 300 60 130

Sometimes fortresses generate without any corridor section because the bridge section cut off where it would go and that takes priority, but fortresses never generate without a lava room.