FloatDoor: backdoors that trigger LLM misbehavior only on specific GPUs and platforms

rickasaurus · x · 2026-10-19

The FloatDoor paper (arXiv) introduces the first input-independent, platform-triggered backdoor against generative LLMs. Exploiting floating-point non-associativity and divergent kernel implementations, two lightweight LoRA adapters amplify inter-platform numerical divergence and bind the platform signature to a malicious task, leaving overall model utility largely intact.

Demonstrated on Qwen3-4B across NVIDIA GPUs, Google TPUs, AWS Graviton, and Alibaba Yitian-710, the attack reliably induces exploitable code vulnerabilities on a chosen target platform — abusing the time-of-check-to-time-of-use gap between model auditing and serving, and highlighting the need for trusted model supply chains.

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