Despite some shoddy defending at times, the hosts came out on top in a seven-goal blitz, with three of the goals coming in the final few minutes.
Goals from Leroy Sané and Serge Gnabry in the 28th and 32nd minutes placed the hosts solidly in control, with injury-plagued United drawing a goal back in the 49th through Rasmus Hojlund’s deflected strike.
United, who had previously lost 3-1 to both Brighton & Hove Albion and Arsenal, have now conceded three goals or more in three straight games for the first time since December 1978.
The visitors had started strongly, with Eriksen coming agonizingly close in the fourth minute, only to have his shot blocked by Bayern keeper Sven Ulreich.
Bayern took the lead thanks to a blunder by United goalie André Onana, who misjudged Sane’s feeble attempt and let it slide past him and into the net.
Hojlund’s deflected effort four minutes after the restart after a fast United passing move gave them optimism, but Bayern quickly snuffed it with Kane’s penalty in the 53rd.
Casemiro scored their third goal in stoppage time, seconds after Bayern replacement Tel had smashed the ball into the roof of the net.
The hosts, who are unbeaten in their past 28 Champions League group stage home meetings, also hit the crossbar in the second half through Sane and Thomas Müller.
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