A 44-year-old man was stabbed in the back in an unprovoked attack on the staircase of a Brooklyn subway station late Wednesday, cops said. 

The assailant knifed the victim from behind on the steps leading to the Sutter Avenue-Rutland Road station in Brownsville around 9:20 p.m., authorities said.

The brute — seen wearing jeans and work boots — didn’t say a word before the attack and did not know the victim, cops said. 

The wounded straphanger was taken to Brookdale University Hospital Medical Center, where he was listed in stable condition, police said. 

The attacker was still on the loose hours later, authorities said.

The attack came about a week after the NYPD revealed that major crime in the city’s subway system is down by about 1 percent compared to last year.

But felony assaults, specifically, were up by 20 incidents through June, according to the department.

Felony assault arrests on the rails also increased by 9% through the first six months of the year, the department said.