It's called the baby-step giant-step algorithm, and it's referred in the report thread to Mozilla:
"They can be recovered near instantly via the baby-step giant-step discrete log algorithm or more simplistically by just generating the 'first' 256 P384 keys."
Oh, I thought you meant "private key up to N bits", not "private key up to the exact value N". In that case, sure, but for non-eMudhra-issued keys BSGS's more relevant complexity figure is O(2^keybits). Unless you've a quantum computer on you, in which case I'm told it's easy-peasy :)