<div class="cp_card">
コンテンツ
  <div class="cp_ribbon12">
    <div class="cp_ribbon">Ribbon</div>
  </div>
</div>

.cp_card {
  position: relative;/*リボンをかけたいコンテンツボックスにセット*/
  width: 300px;
  height: 300px;
  background: #ffffff;
  margin: auto;
  padding: 70px 5px 0;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/*リボンの設定*/
.cp_ribbon12 {
  position: absolute;
  top: 15px;
  left: -10px;
  width: calc(100% + 20px);
}
/*リボンの帯部分*/
.cp_ribbon12 .cp_ribbon {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 40px;
  color: #ffffff;
  background: #F48FB1;
  z-index: 0;
}
/*カットされたリボンの共通設定*/
.cp_ribbon12:before,
.cp_ribbon12:after {
  position: absolute;
  bottom: -10px;
  content: '';
  width: 0;
  height: 0;
  border-width: 20px 20px;
  border-style: solid;
  border-color: #F06292 #F06292 #F06292 transparent;
  z-index: -1;
}
.cp_ribbon12:before {
  left: -30px;
}
.cp_ribbon12:after {
  right: -30px;
  transform: scale(-1, 1);/*左右反転*/
}
/*リボンの影の共通設定*/
.cp_ribbon12 .cp_ribbon:before,
.cp_ribbon12 .cp_ribbon:after {
  position: absolute;
  bottom: -10px;
  content: '';
  width: 0;
  height: 0;
  border-top: 10px solid #C2185B;
  border-left: 10px solid transparent;
}
.cp_ribbon12 .cp_ribbon:before {
  left: 0;
}
.cp_ribbon12 .cp_ribbon:after {
  right: 0;
  transform: scale(-1, 1);/*左右反転*/
}