Brazilian forward Rafinha and South Korean internationals Kim Shin-wook and Lee Keun-ho scored the goals as the visitors overcame the problematic, sandy pitch at the Jar Stadium in Tashkent to maintain their unbeaten run in this season's tournament.
With the winners of the Ulsan-Bunyodkor tie drawn to host the November 10 final against either Al Ittihad or Al Ahli, the Koreans will be heavy favourites to continue the country's strong showing in Asia's premier club tournament after another eye-catching attacking display.
That scenario didn't look likely early on in Uzbekistan with the home side, who had won all three matches against Korean opponents in this season's tournament, starting brightly and taking a deserved lead on five minutes.
Slovak midfielder Jan Kozak was allowed too much space down the right to pull back a cross sharply which Jovlon Ibrokhumov guided into the corner of the net from the edge of the area after a well-timed run.
Bunyodkor came close to doubling their lead in the 23rd minute when the lively Ibrokhumov again found space in the box but couldn't steer his header wide of the goalkeeper.
Ulsan were sitting deep, under pressure from the hosts, but came up with a counter-attack equaliser through the dangerous Rafinha on the half-hour mark.
Lee Keun-ho broke down the right and cut inside to find Rafinha on the edge of the area and the Brazilian neatly chested the ball down and away from his marker before firing a low left-foot shot just inside the near post.
The goal sparked an entertaining, end-to-end remainder of the half with Ulsan enjoying the better of the chances.
Bunyodkor goalkeeper Ignatiy Nesterov was on hand to parry a close-range header from midfielder Kim Seung-yong, while Ulsan striker Kim Shin-wook should have done better with a free header from 12 metres out.
Kim Shin-wook faired much better with a second header after the interval.
The lanky striker darted to the near post to meet an inswinging corner from Kim Seung-yong and powerfully headed Ulsan in front in the 53rd minute.
Uzbek midfielder Lutfulla Turaev twice went close to finding the equaliser with left foot shots before another set piece from Kim Seung-yong set up Ulsan's third.
The midfielder clipped in a free kick which the speedy Lee Keun-ho flicked into the top corner of Nesterov's net with 18 minutes remaining.
The Uzbeks were gifted the opportunity to cut the deficit when they were awarded a penalty three minutes later after experienced Korean centre back Kwak Tae-hwi handled in the box, but Jasur Khasanov hit the spot kick against the post.
In the other tie played on Monday, Naif Hazazi scored the only goal as twice champions Al Ittihad claimed a 1-0 win in the first leg of their all-Saudi Arabian semi-final against Al Ahli.
Hazazi bundled in a scrappy goal in the 67th minute, his eighth of the campaign, to leave Al Ittihad in pole position to advance from the return leg next week.