Q: Given the following code slice:
```
1 static UINT ExtractRunLengthRegularFgBg(const BYTE* pbOrderHdr, const BYTE* pbEnd, UINT32* advance)
9 	runLength = (*pbOrderHdr) & g_MaskRegularRunLength;
10 	if (runLength == 0)
12 		if (!buffer_within_range(pbOrderHdr, 1, pbEnd))```
which has a CWE-125 vulnerability at line:
```
12 		if (!buffer_within_range(pbOrderHdr, 1, pbEnd))
```
Please analyze the root cause of the vulnerability.