TinyUSB before 0.20.1 contains an integer underflow vulnerability in the HID host report descriptor parser tuh_hid_parse_report_descriptor() in src/class/hid/hid_host.c that allows a malicious USB device to trigger an out-of-bounds read by subtracting an item size from the remaining descriptor length without validating the item fits within the remaining buffer. Attackers can present a crafted USB device with a truncated report descriptor causing the uint16_t desc_len value to underflow, resulting in out-of-bounds memory reads and denial of service on the host system.