SK Hynix DDR5 DIMMs (manufactured 2021-01 through 2024-12): Rowhammer bit flips on DDR5, which had been assumed out

Impact

Rowhammer bit flips on DDR5, which had been assumed out of reach because of on-die ECC and improved TRR. Affects SK Hynix DDR5 DIMMs produced between January 2021 and December 2024 - a very large share of DDR5 installed in AI host nodes bought in that window. Impact is integrity of host memory, with the usual escalation to privilege via page-table corruption.

Who can reach it

Local attacker on the node. High attack complexity, low privileges - a tenant workload with sustained memory access is the model.

What to do

Take an inventory of DIMM vendor and date code across the fleet (dmidecode -t memory) before anything else, because the exposure is specific. Mitigation guidance is to raise the DRAM refresh rate - tripling it substantially raises the bar at a measurable memory-bandwidth cost - which is a BIOS-level change requiring drain and reboot per node. There is no microcode or OS patch. Monitor correctable ECC error rates as the detection signal.

References