BACnet Protocol Stack through 0.8.6 has a segmentation fault leading to denial of service in BACnet APDU Layer because a malformed DCC in AtomicWriteFile, AtomicReadFile and DeviceCommunicationControl services. An unauthenticated remote attacker could cause a denial of service (bacserv daemon crash) because there is an invalid read in bacdcode.c during parsing of alarm tag numbers.