Root Cause Analysis: Looking at the given vulnerable code line and its context, the CWE-787 (out-of-bounds write) vulnerability exists in the code because the variable `fl->num_fh` is used to allocate memory for the `fl->fh_array` without checking if `fl->num_fh` is 0. If `fl->num_fh` is 0, then allocating memory for `fl->fh_array` with `fl->num_fh * sizeof(nfs_fh *)` will result in an out-of-bounds write vulnerability, which is CWE-787.