AIKIDO-2026-182147

TL;DR

rapidhash's RandomState derives each hasher's seed from a thread-local counter that starts at zero combined with the current stack address as its only per-thread entropy. When the operating system recycles thread stacks, newly spawned threads observe the same stack address and therefore compute duplicate, predictable seeds, and on targets without ASLR or ambient entropy the seed is effectively deterministic. An attacker who can predict the seed can craft keys that all collide in a HashMap or HashSet, forcing worst-case quadratic behavior and denial of service. The fix initializes each thread's seed counter from a global thread counter mixed with a process-wide random seed and adds getrandom-based entropy paths for no_std and wasm targets.