According to the ARM® security team, Spectre-BSE exploits a micro-architectural mechanism that equips an adversary with a weak form of control over the victim’s branch history despite existing protections.
This can lead to exploitative control of indirect branches and potentially to data exfiltration. This issue affects ARM Cortex®-A72 (revisions prior to r1p0), Cortex-A73 and Cortex-A75.