Ajman took the lead after 14 minutes through Ivorian attacker Boris Kabi, only for Luis Jimenez to equalise for the visitors.
The league leaders struggled to break down the home defence and looked to be on their way to a third consecutive away game without a win until they were handed a spot kick deep into stoppage time.
Ajman have now dropped into relegation zone by virtue of Dubai's 1-1 draw with Al Wahda in a game that saw both teams reduced to 10 men in the second half.
Al Shaab remain bottom following a 1-0 loss at Al Sharjah, midfielder Kim Jung-Woo's second-half striker condemning the strugglers to their ninth defeat of the campaign shortly after Essa Ali had been sent off for the visitors.
Mohamed Naser's 92nd-minute equaliser earned Al Wasl a 1-1 draw against Bani Yas, who have now gone four league games without a win, despite Haboush Saleh Habou's opener in first-half injury time.
