CVE-2019-13916

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.