Despite AMD’s growing market share with Zen CPUs, Rowhammer attacks were absent due to challenges in reverse engineering DRAM addressing, synchronizing with refresh commands, and achieving sufficient row activation throughput.  Researchers addressed these through ZENHAMMER, the first Rowhammer attack on recent AMD CPUs. ZENHAMMER reverse engineers non-linear addressing uses crafted access patterns for synchronization, and schedules instructions carefully to increase throughput while bypassing mitigations.  Evaluations demonstrated ZENHAMMER finding bit flips on 7 out of 10 DDR4 devices on Zen 2/3 CPUs, enabling Rowhammer exploitation on current AMD platforms.

Source: GBHackers