In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: Fix queuing commands when HCI_UNREGISTER is set hci_cmd_sync_queue shall return an error if HCI_UNREGISTER flag has been set as that means hci_unregister_dev has been called so it will likely cause a uaf after the timeout as the hdev will be freed.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.