A: Root Cause Analysis: Looking at the given vulnerable code line, the CWE-125 (Out-of-bounds Read) vulnerability exists in the code because the index `i` is used to access the `byte` array without checking if it is within the valid range of indices for the array. If `i` is less than 0 or greater than or equal to the size of the `byte` array, it will lead to an out-of-bounds read vulnerability, which is CWE-125.