The vulnerability stems from manual implementations of Send/Sync traits for ButtplugFutureStateShared<T> that didn't respect T's thread-safety traits. This allowed the struct to be considered thread-safe even when containing !Send/!Sync types, enabling data races. The RustSec advisory explicitly states the fix involved removing these manual implementations to rely on auto trait derivation, confirming these trait implementations were the root cause. While specific file paths aren't provided, the structural analysis of trait implementations matches the vulnerability description with high confidence.