It happens, because "wait(timeout)" is not in the loop. Object#wait(long) is explicit about that: "A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops..."

https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-

Impact:

• AsyncFutureImpl is being used explicitly in JarCacheSupport. Jar resolution with a timeout may fail due to the issue
• The class is overridden in Jenkins Core's public API, e.g. hudson.model.queue.FutureImpl. It's hard to estimate risks, but it looks bad.