AMD, Apple, Qualcomm GPUs leak AI data in LeftoverLocals attacks

LeftoverLocals (CVE-2023-4969) is a GPU local-memory isolation flaw discovered by Trail of Bits that allows a malicious GPU kernel to read residual local memory from other kernels—potentially exposing LLM inputs, outputs, weights and intermediate data. A public PoC shows large data recoveries (up to hundreds of MB per query in some setups); vendors have issued partial fixes but several GPU models remain vulnerable. Recommended mitigations include automatic local-memory clearing between kernel calls, avoiding multi-tenant GPUs for sensitive workloads, and applying vendor patches where available.