Mustafina holds a narrow lead over Viktoria Komova, who fell on beam, 59.335-59.234.
Both gymnasts recorded their highest mark on uneven bars, with Komova showing a new routine worth a 7.0, including a piked Tkatchev release and a double-double dismount (16.134). Mustafina wasn't far behind, scoring 15.834.
Mustafina stuck a double-twisting Yurchenko on vault (14.667) and gave away only small errors on beam (14.667) and floor (14.167). Komova hit three great events (14.8 vault, 14.3 floor), before missing a layout on beam (14.0).
Komova also did a double-twisting Yurchenko, but it has been reported that both she and Mustafina are doing Amanars in training. Both gymnasts have previously competed the vault; Mustafina injured her knee doing the skill.
Veteran Ksenia Afanasyeva sits in third, still getting back to form in 2012 after winning the floor exercise gold at last year's World Championships. Afanasyeva watered down her tumbling (14.067) and fell on her vault (13.267), but showed a stable routine on balance beam (14.467).
2004 and 2008 Olympian Anna Pavlova continues to train, despite not being named to the national team this year. Pavlova is fourth all-around and put up good scores on vault (14.467) and beam (14.4).
Two gymnasts on the bubble for London, Maria Paseka and Anna Dementyeva did themselves favors by hitting their strongest events. Paseka showed an Amanar (15.8), while Dementyeva posted the highest score on her specialty, the balance beam (14.867).
Anastasia Sidorova, who competed for Russia at the European Championships this year, fell twice from balance beam (12.434).
Top Russian gymnast Anastasia Grishina sat out of the competition, resting a leg injury.
The Russian Cup concludes with the all-around finals on Friday.