=== What is the potential impact?

An attacker with the capability to insert an arbitrary duration into a thread
suspension operation could suspend the corresponding thread for a long time.
Depending on the application's architecture and the thread handling logic, this
can lead to a complete Denial of Service of the application.

Indeed, if the number of threads, either created by the application or allocated
by a web server, is limited, the attacker will be able to suspend all of them at
the same time. Without any remaining thread to handle actions, the application
might badly answer, be slowed down, or become completely irresponsive.