Buhai, who has never posted a top-25 finish at a major championship, will now need to come from behind on Sunday having led after rounds one and two, while Shibuno is on course to become only the second Japanese victor of a women's major. "I came in wanting to make the cut, so right now I feel like I'm doing something very incredible". "It's just another tournament", said Buhai, whose best previous British Open finish was a tie for 30th in 2017.
While the youngster completed a round of 67 by picking up shots at four of the last five holes, long-time leader Ashleigh Buhai faltered down the stretch, bogeying the 12th, 13th and 16th on her way to a 72.
The 20-year-old Shibuno, a rookie on the Japan LPGA Tour who is making her LPGA Tour and major championship debut, hit six birdies in the final nine holes of the third round for a 14-under 202.
Salas birdied the first four holes to challenge for the lead but could add only one more the rest of the way.
South Korea's Park Sung-hyun is in third place, three strokes behind Shibuno, with compatriot and last week's Evian Championship major victor Ko Jin-young in a three-way tie for fourth with Americans Morgan Pressel and Lizette Salas. "I loved it out there today", Hall said.
"I sometimes like being the underdog", she said. A win at Woburn would put Ko on that elite list, having won the 2019 ANA Inspiration and last week's Evian Championship.
Brice Garnett was a stroke back after a 64, and six players - including 2011 Wyndham victor Webb Simpson and first-round co-leader Sungjae Im - were at 9 under.
The three-time Ladies European Tour victor picked up her first birdie of the day on the par-five second before seven straight pars to finish the first nine at one-under. Chako Higuchi won the Women's PGA Championship in 1977.
American Lizette Salas stands alone in third place at 8 under after firing a bogey-free round of 67.
"I knew if it went in, I would most likely win, and it went in, " Heath said. "When I play Solheim (Cup) I prefer playing in America, where the crowd's cheering against you". She's also six back after carding a 70.
Canon Claycomb, a 17-year-old Alabama recruit from Bowling Green, Kentucky, shot a 66 to finish second.