Sussex Police are appealing for witnesses following the incident, which happened at 11.50pm in Baldslow Road on Sunday (June 26).
Police said a man aged 18 was assaulted and sustained serious injuries.
He was taken to hospital where he currently remains.
Officers have released CCTV images of two men they wish to speak with in connection with the assault.
Police said they were seen interacting with the victim in Queens Road, minutes before the assault took place.
They are both described as white men in their late teens or early 20s, both with short dark hair, 6ft tall, and wearing white T-shirts.
One wore grey tracksuit bottoms and black trainers and carried a small black bag. The other wore dark trousers and black and white trainers.
Witnesses or anyone with CCTV in the area at the time is asked to report it to police.
Contact police on 101, quoting serial 1482 of 26/06.