PC-DDR4 / LPDDR4X DRAM - Target Row Refresh mitigation: Non-uniform Rowhammer patterns triggered bit flips on every one

Impact

Non-uniform Rowhammer patterns triggered bit flips on every one of the 40 DDR4 modules the researchers tested, including modules whose TRR implementation had resisted TRRespass. Scored 9.0 with a changed scope. Same operator consequence as TRRespass: an integrity attack on host memory reachable from tenant code.

Who can reach it

Local code on the node able to generate the access pattern. Scored AV:Network by the reporters because remote code paths (JavaScript, network stacks) can drive memory access, but the realistic datacenter path is a tenant workload.

What to do

No vendor patch. Use ECC and alert on correctable-error rate rather than only on uncorrectable errors; enable increased refresh rate or RFM in BIOS if your platform exposes it, accepting a small memory-bandwidth cost. Cost: BIOS change means drain and reboot. Effectively UNPATCHABLE.

References