Police Scotland was alerted to the attack outside a flat in Torphin Crescent, Greenfield, at about 8.50pm on Wednesday.
The victim was taken to Glasgow Royal Infirmary with a cut to his face but has been unable to provide any information about his attacker.
Detective Constable Craig Hartley said: “A man has received a serious injury to his face and I am appealing to local residents who may have seen or heard something to get in touch with us.
“The motive for the attack is unknown and we are trying to establish exactly what has happened.
“If you have any information, please pass your information on, it could prove vital in helping us find whoever is responsible for this attack.”
Officers have been carrying out door-to-door enquiries and are gathering CCTV footage.