SCTP_STATIC int sctp_listen_start(struct sock *sk, int backlog)
{
	struct sctp_sock *sp = sctp_sk(sk);
	struct sctp_endpoint *ep = sp->ep;
	struct crypto_hash *tfm = NULL;
	char alg[32];

	/* Allocate HMAC for generating cookie. */
	if (!sp->hmac && sp->sctp_hmac_alg) {
		sprintf(alg, "hmac(%s)", sp->sctp_hmac_alg);
		tfm = crypto_alloc_hash(alg, 0, CRYPTO_ALG_ASYNC);
		if (IS_ERR(tfm)) {
			net_info_ratelimited("failed to load transform for %s: %ld\n",
					     sp->sctp_hmac_alg, PTR_ERR(tfm));
			return -ENOSYS;
		}
		sctp_sk(sk)->hmac = tfm;
	}

	/*
	 * If a bind() or sctp_bindx() is not called prior to a listen()
	 * call that allows new associations to be accepted, the system
	 * picks an ephemeral port and will choose an address set equivalent
	 * to binding with a wildcard address.
	 *
	 * This is not currently spelled out in the SCTP sockets
	 * extensions draft, but follows the practice as seen in TCP
	 * sockets.
	 *
	 */
	sk->sk_state = SCTP_SS_LISTENING;
	if (!ep->base.bind_addr.port) {
		if (sctp_autobind(sk))
			return -EAGAIN;
	} else {
		if (sctp_get_port(sk, inet_sk(sk)->inet_num)) {
			sk->sk_state = SCTP_SS_CLOSED;
			return -EADDRINUSE;
		}
	}

	sk->sk_max_ack_backlog = backlog;
	sctp_hash_endpoint(ep);
	return 0;
}

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.