Barack Obama coming inches away from an armed stranger in a Hollywood alleyway is the latest stunning lapse of Secret Service security — an absolutely shocking scene that played out last weekend … TMZ has learned.

The former president was sitting in the back seat of his SUV Saturday around 7:30 PM outside hot spot restaurant Mother Wolf — and that’s when the armed man approached the vehicle, in his capacity as a security guard for a bar mitzvah going on upstairs from the restaurant.