An issue was discovered in the Bluetooth component of the Cypress (formerly owned by Broadcom) Wireless IoT codebase. Extended Inquiry Responses (EIRs) are improperly handled, which causes a heap-based buffer overflow during device inquiry. This overflow can be used to overwrite existing functions with arbitrary code. The Reserved for Future Use (RFU) bits are not discarded by eir_handleRx(), and are included in an EIR's length. Therefore, one can exceed the expected 240 bytes, which leads to a heap-based buffer overflow in eir_getReceivedEIR() called by bthci_event_SendInquiryResultEvent(). In order to exploit this bug, an attacker must repeatedly connect to the victim's device in a short amount of time from different source addresses. This will cause the victim's Bluetooth stack to resolve the device names and therefore allocate buffers with attacker-controlled data. Due to the heap corruption, the name will be eventually written to an attacker-controlled location, leading to a write-what-where condition.
The product writes data past the end, or before the beginning, of the intended buffer.