Cypress CYW20735B1

An issue was discovered in Cypress (formerly Broadcom) WICED Studio 6.2 CYW20735B1 and CYW20819A1. As a Bluetooth Low Energy (BLE) packet is received, it is copied into a Heap (ThreadX Block) buffer. The buffer allocated in dhmulp_getRxBuffer is four bytes too small to hold the maximum of 255 bytes plus headers. It is possible to corrupt a pointer in the linked list holding the free buffers of the g_mm_BLEDeviceToHostPool Block pool. This pointer can be fully controlled by overflowing with 3 bytes of packet data and the first byte of the packet CRC checksum. The checksum can be freely chosen by adapting the packet data accordingly. An attacker might be able to allocate the overwritten address as a receive buffer resulting in a write-what-where condition. This is fixed in BT SDK2.4 and BT SDK2.45.

The Bluetooth Classic implementation in the Cypress CYW920735Q60EVB does not properly handle the reception of continuous unsolicited LMP responses, allowing attackers in radio range to trigger a denial of service and restart (crash) of the device by flooding it with LMP_AU_Rand packets after the paging procedure.

The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 does not properly handle the reception of a malformed LMP timing accuracy response followed by multiple reconnections to the link slave, allowing attackers to exhaust device BT resources and eventually trigger a crash via multiple attempts of sending a crafted LMP timing accuracy response followed by a sudden reconnection with a random BDAddress.

The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 devices does not properly handle the reception of LMP_max_slot with a greater ACL Length after completion of the LMP setup procedure, allowing attackers in radio range to trigger a denial of service (firmware crash) via a crafted LMP packet.

The Bluetooth Classic implementation in the Cypress WICED BT stack through 2.9.0 for CYW20735B1 devices does not properly handle the reception of LMP_max_slot with an invalid Baseband packet type (and LT_ADDRESS and LT_ADDR) after completion of the LMP setup procedure, allowing attackers in radio range to trigger a denial of service (firmware crash) via a crafted LMP packet.