BarnOwl before 1.6.2 does not check the return code of calls to the (1) ZPending and (2) ZReceiveNotice functions in libzephyr, which allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via unknown vectors.
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.