Azure RTOS USBX is a USB host, device, and on-the-go (OTG) embedded stack. Prior to version 6.1.11, he USBX DFU UPLOAD functionality may be utilized to introduce a buffer overflow resulting in overwrite of memory contents. In particular cases this may allow an attacker to bypass security features or execute arbitrary code.

The implementation of ux_device_class_dfu_control_request function does not assure that a buffer overflow will not occur during handling of the DFU UPLOAD command. When an attacker issues the UX_SLAVE_CLASS_DFU_COMMAND_UPLOAD control transfer request with wLenght larger than the buffer size (UX_SLAVE_REQUEST_CONTROL_MAX_LENGTH, 256 bytes), depending on the actual implementation of dfu - ux_slave_class_dfu_read, a buffer overflow may occur. In example ux_slave_class_dfu_read may read 4096 bytes (or more up to 65k) to a 256 byte buffer ultimately resulting in an overflow.

Furthermore in case an attacker has some control over the read flash memory, this may result in execution of arbitrary code and platform compromise. A fix for this issue has been included in USBX release 6.1.11. As a workaround, align request and buffer size to assure that buffer boundaries are respected.