Unheeded warnings and a series of communications and security lapses allowed a man recruited to help track down Osama bin Laden's deputy get into a U.S. base in Afghanistan and kill seven CIA operatives, an investigation concluded.

A Central Intelligence Agency task force's six-month probe of the December suicide bombing at Khost stopped short of blaming any individuals, but found systemic problems. CIA Director Leon Panetta said the lapses are being addressed and security rules at agency bases have been tightened.

The...