It turns out that NVIDIA GPUs are susceptible to Spectre after all (but not Meltdown). They have released new drivers to mitigate the vulnerability:
That’s a bit misleading. From the actual NVidia release notes:
"We believe our GPU hardware is immune to the reported security issue. As for our driver software, we are providing updates to help mitigate
the CPU security issue."
Like any software, their drivers are a target, but their GPUs aren’t susceptible.