A vulnerability in the Constrained Application Protocol (CoAP) implementation of Cisco IoT Field Network Director could allow an unauthenticated remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient input validation of incoming CoAP traffic. An attacker could exploit this vulnerability by sending a malformed CoAP packet to an affected device. A successful exploit could allow the attacker to force the CoAP server to stop, interrupting communication to the IoT endpoints.