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GPUThor Cracks Nvidia ECC, Reaches Root Shell
7 Sep
Summary
- GPUThor attack bypasses Nvidia's ECC protection on GPUs.
- The exploit grants an unprivileged CUDA program root shell access.
- Four Nvidia Ampere workstation GPUs with GDDR6 memory are affected.
Researchers have unveiled GPUThor, a novel Rowhammer attack capable of circumventing the Error Correcting Code (ECC) implemented by Nvidia. This development challenges Nvidia's prior assertions that ECC was a robust defense against Rowhammer threats. The attack specifically targets four Nvidia Ampere workstation GPUs equipped with GDDR6 memory: the RTX A4000, A4500, A5000, and A6000.
The GPUThor technique transforms an unprivileged CUDA program into a root shell on the host system. Previous Rowhammer attacks were rendered ineffective upon enabling ECC. However, GPUThor leverages non-uniform hammering, a method that exploits weaknesses in memory coalescing and Target Row Refresh (TRR) mitigations, to achieve significantly higher hammering intensity compared to earlier attacks. This advancement places GPU Rowhammer attacks on par with their CPU counterparts in terms of potential impact.
While ECC and TRR do reduce bit flips, GPUThor's non-uniform approach can still cause double-bit and triple-bit errors, which ECC 'fixes' with incorrect values. On an RTX A6000 with ECC enabled, the attack reportedly causes a GPU reset every two hours, leading to system instability and the card eventually flagging itself for return. The researchers disclosed the vulnerability to Nvidia, Google, Microsoft, and AWS on April 29, 2026, and plan to release code on November 15, 2026.
