In the Linux kernel, the following vulnerability has been resolved:

usb: xhci: Fix NULL pointer dereference on certain command aborts

If a command is queued to the final usable TRB of a ring segment, the
enqueue pointer is advanced to the subsequent link TRB and no further.
If the command is later aborted, when the abort completion is handled
the dequeue pointer is advanced to the first TRB of the next segment.

If no further commands are queued, xhci_handle_stopped_cmd_ring() sees
the ring pointers unequal and assumes that there is a pending command,
so it calls xhci_mod_cmd_timer() which crashes if cur_cmd was NULL.

Don't attempt timer setup if cur_cmd is NULL. The subsequent doorbell
ring likely is unnecessary too, but it's harmless. Leave it alone.

This is probably Bug 219532, but no confirmation has been received.

The issue has been independently reproduced and confirmed fixed using
a USB MCU programmed to NAK the Status stage of SET_ADDRESS forever.
Everything continued working normally after several prevented crashes.

https://git.kernel.org/stable/c/0ce5c0dac768be14afe2426101b568a0f66bfc4d

https://git.kernel.org/stable/c/1e0a19912adb68a4b2b74fd77001c96cd83eb073

https://git.kernel.org/stable/c/4ff18870af793ce2034a6ad746e91d0a3d985b88

https://git.kernel.org/stable/c/ae069cd2ba09a2bd6a87a68c59ef0b7ea39cd641

https://git.kernel.org/stable/c/b649f0d5bc256f691c7d234c3986685d54053de1