dissect_dch_dl_synchronisation(proto_tree *tree, packet_info *pinfo, tvbuff_t *tvb, int offset)
{
    /* CFN control */
    guint cfn = tvb_get_guint8(tvb, offset);
    proto_tree_add_item(tree, hf_fp_cfn_control, tvb, offset, 1, ENC_BIG_ENDIAN);
    offset++;

    col_append_fstr(pinfo->cinfo, COL_INFO, " CFN = %u", cfn);

    return offset;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.