The local man was subjected to an attack on Acomb Road, by the corner with Fairfax Court, at about 7.40pm on Monday 21 January 2013.
He was taken to York District Hospital by ambulance but has now been transferred to Leeds General Infirmary for specialist treatment.
A 19-year-old man and a 16-year-old boy have been arrested in connection with the investigation. They remain in police custody for questioning.
Detective Inspector Ian Dyer, of York CID, said:
This is a very serious incident which has left a man critically ill in hospital.
We are providing support to his family at this distressing time while we investigate the full circumstances surrounding the assault.
DI Dyer is urging residents in York who may have information to come forward to the police without delay.
Detective Inspector Ian Dyer added:
It is vitally important that all witnesses to the assault do the right thing and contact the investigation team as soon as possible.
We need to piece together what happened on Monday evening, including what the individuals involved were doing in the build-up to the incident. Even the smallest item of information could be crucial.
If you can help the investigation then I urge you to contact the police straight away. Information can also be passed to Crimestoppers if you would prefer not to give your name.
Please call North Yorkshire Police on 101, select option 2, and ask for York CID.
If you wish to remain anonymous, information can be passed to Crimestoppers on 0800 555111.
Please quote reference number 12130011464.