New 'GPUThor' Rowhammer attack bypasses ECC on Nvidia workstation GPUs

Researchers from the University of Toronto have disclosed a new Rowhammer attack vector dubbed 'GPUThor' that specifically targets Nvidia Ampere-generation workstation GPUs, including the RTX A4000, A4500, A5000, and A6000. The attack utilizes non-uniform hammering to bypass Target Row Refresh (TRR) mitigations and, for the first time, successfully defeats Error Correction Code (ECC) memory protections. By exploiting these vulnerabilities, the researchers demonstrated the ability to gain root shell access on the host system from an unprivileged CUDA program. While the team notified Nvidia, Google, Microsoft, and AWS of the findings in April 2026, no patches or CVEs have been issued yet. The researchers plan to release the attack code on November 15, 2026. This discovery highlights a significant escalation in GPU-based security threats, bringing them to a level of intensity previously associated only with CPU-based Rowhammer attacks.