All we know is a leak to Bojan Pancevski, Germany correspondent for WSJ. He writes, “U.S. Officials Say Huawei Can Covertly Access Telecom Networks.” The U.S. is almost certainly blowing this up; both Germany and the UK confirmed Huawei purchases after the U.S. shared the classified information.
Neither Pancecski nor anyone speaking publicly has seen evidence this is a deliberate “backdoor,” as the U.S. government called it. Nor has the U.S. found any evidence its been used for spying. Neither can be ruled out because the evidence is hidden.
More likely, the U.S. has discovered a way in. Vint Cerf explains there are two types of systems: those already hacked or those that will be.
U.S. espionage spends $50 billion a year, supporting literally tens of thousands of (often brilliant) people dedicated to infiltration. Huawei gear is target #1.
It would be surprising if the U.S. didn’t find a way in that could be the real story.