Q: Given the following code slice:
```
1 static int qca_read_fw_build_info(struct hci_dev *hdev)
5 	char cmd, build_label[QCA_FW_BUILD_VER_LEN];```
which has a CWE-125 vulnerability at line:
```
5 	char cmd, build_label[QCA_FW_BUILD_VER_LEN];
```
Please analyze the root cause of the vulnerability.