Azure RTOS USBX Host PIMA vulnerable to read integer underflow with buffer overflow

CVE-2022-39293

What is CVE-2022-39293?

Azure RTOS USBX is a high-performance USB host, device, and on-the-go (OTG) embedded stack, that is fully integrated with Azure RTOS ThreadX. The case is, in _ux_host_class_pima_read, there is data length from device response, returned in the very first packet, and read by L165 code, as header_length. Then in L178 code, there is a “if” branch, which check the expression of “(header_length - UX_HOST_CLASS_PIMA_DATA_HEADER_SIZE) > data_length” where if header_length is smaller than UX_HOST_CLASS_PIMA_DATA_HEADER_SIZE, calculation could overflow and then L182 code the calculation of data_length is also overflow, this way the later while loop start from L192 can move data_pointer to unexpected address and cause write buffer overflow. The fix has been included in USBX release 6.1.12. The following can be used as a workaround: Add check of header_length: 1. It must be greater than UX_HOST_CLASS_PIMA_DATA_HEADER_SIZE. 1. It should be greater or equal to the current returned data length (transfer_request -> ux_transfer_request_actual_length).

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