The root cause of the CWE-190 (Integer Overflow or Wraparound) vulnerability in this code is:

1. Unchecked arithmetic operations: The calculation `nXDst * dstBytesPerPixel + nYDst * nDstStep` is performed without any bounds checking or overflow detection.

2. Use of unsigned integers: While UINT32 is used, which prevents negative values, it doesn't prevent overflow when the result exceeds the maximum value (2^32 - 1).

3. Potential for large input values: If nXDst, dstBytesPerPixel, nYDst, or nDstStep are large, their products or sum could exceed UINT32's maximum value.

4. Direct use in pointer arithmetic: The result is immediately used to offset pDstData, which could lead to accessing memory outside the intended buffer if an overflow occurs.

To mitigate this vulnerability, the code should implement checks to ensure that the arithmetic operations don't result in an overflow before performing the calculation and using the result for pointer arithmetic.