MidiManagerWin uses a similar instance_id mechanism to the TaskService implementation to ensure that delayed tasks are only executed if the MidiManager instance that they were scheduled on is still alive.
However, this instance_id is an int, and there is no check that it hasn't overflowed, unlike in the linux and mac implementations (MidiManagerAlsa), see https://cs.chromium.org/chromium/src/media/midi/midi_manager_alsa.cc?rcl=282aae73b9d2c1cbf12d3c39a8d3d2612e4b1876&l=175
This means that if (for example) a delayed sendData on a stale MidiManagerWin instance is queued up, and then the instance id is wrapped, this will trigger a use-after-free when that task triggers.
I've attached a PoC (using the MojoJS bindings) that demonstrates the issue in a more convenient amount of time for testing if you patch the variable `static int id` in IssueNextInstanceId to a `static short`. Runtime will also be shorter if you run the PoC directly after booting; it also has to synchronise clocks with the system clock, and I haven't put any work into making that quick.
Proof of Concept: