KVGuard: Catching the KV cache bug behind Cloudflare's GLM leak
In October 2026, Cloudflare disclosed that 155 responses from its GLM-5.3 model on Workers AI leaked pieces of other users' prompts and outputs. Nothing crashed, nothing was logged, and every response returned HTTP 200 (OK). The model was not at fault: the serving engine, SGLang, let a request read KV cache memory it never wrote.
We built KVGuard, a KV cache sanitizer for LLM serving systems. It catches this exact bug, and every other code path that ends in the same bad read.




