Police are investigating an assault in Court Square Brow, near Carlisle railway station, at around 2:45am on 14 September.
The victim, a 24-year-old man from Carlisle, sustained serious facial injuries.
A Cumbria Police spokesman said: “Police are seeking a man, about 6ft tall, with light-coloured hair, wearing a light-coloured shirt, who was seen carrying a black bag at the time of incident.
“Officers are appealing for anyone that has witnessed this incident, has dash-cam or CCTV footage or has seen anyone leaving the area matching this description, to come forward.”
Anyone with information is encouraged to contact DC 2667 on 101, quoting incident number 24 of 14 September.
Alternatively you can call Crimestoppers, anonymously, on 0800 555 111.