GPUThor Rowhammer Attack Compromises Nvidia's High-End Workstation GPUs

Nvidia's high-end workstation graphics processing units (GPUs) have been compromised by a new Rowhammer attack called GPUThor. Researchers at the University of Toronto discovered that four Ampere-generation cards with GDDR6 memory - the RTX A4000, A4500, A5000 and A6000 - are vulnerable to the attack.

The researchers used non-uniform hammering, a technique that exploits a weakness in the GPU's memory coalescing and Target Row Refresh (TRR) mitigations. This allowed them to deliver 6.6 times the hammering intensity of prior attacks, making it possible to break the error correction mechanism that Nvidia has been recommending as a defense against this type of attack.

The attack targets unprivileged CUDA programs and can turn them into root shells on the host. The researchers found that GPUThor produced 72,000 to 377,000 bit flips per gigabyte across four Ampere-based cards, with the RTX A5000 being the most vulnerable.