Police said the 27-year-old victim heard a knock at the door of his home in Brucehill Road, Dumbarton at 00:15.
When he answered it, he was "violently attacked" by three men who he did not know.
Officers said that images of the men have been captured on CCTV cameras in the area and they appealed for help in tracing them.
One of the men walked with a limp and they were all in their 30s.
Det Sgt Fiona Macarthur said: "This man was violently attacked on his own doorstep and it is absolutely crucial that we trace the people responsible as soon as possible.
"I would like to speak to anyone who was in the area in the early hours of this morning and saw three men or anything suspicious."

Wholesale prices have dropped and motoring organisations have suggested this merits reduced pump prices.
Tesco and Morrisons are cutting prices by 2p a litre on Friday, and Asda and Sainsbury's said they would reduce prices by up to 2p a litre on Saturday.
But drivers are being warned that prices can vary in different areas.
The average UK price for a litre of unleaded petrol was 118.83p on Thursday, and 120.88p for a litre of diesel, according to the latest figures from Experian Catalist.
Ten days earlier, the average unleaded price was 120p a litre, and diesel cost 122.06p.
The oil price and wholesale prices fell sharply at the start of March, and motoring organisations have argued that this should have been feeding through to another 2p cut per litre in prices at the pumps.
The RAC said motorists could feel "aggrieved" that prices had not fallen further, earlier.
Asda said it had dropped prices twice in two weeks, and had a national price cap to ensure motorists were dealt with equitably. Morrisons said it had also made a second cut in two weeks.
Tesco is dropping petrol and diesel prices by 2p a litre over the course of Friday afternoon at all its outlets, followed by Sainsbury's on Saturday.
Luke Bosdet, of the AA, said that there was general concern that so-called supermarket fuel price wars did not actually benefit all drivers across the country.
He claimed prices fell the most in areas where there were a range of supermarkets located close to each other. In other areas with less competition, the same cuts were not as likely to be seen.
"We would urge motorists to look around to find a better price. There are petrol price apps that can help," he said.
A man is being treated for stab wounds after he was attacked by three men on his own doorstep.
[NEXT_CONCEPT]
Motorists will see an acceleration in fuel price cuts over the weekend as supermarkets take up to 2p off a litre of petrol and diesel.