Motor.NET before 0.19.0 contains an uncaught exception vulnerability in JsonNetDeserializer.Deserialize that allows a remote attacker who can publish to a consumed queue or topic to crash the service permanently by sending structurally valid JSON that does not match the handler's expected type. Attackers can exploit the fact that JsonSerializationException is not caught alongside JsonReaderException and InvalidCastException, causing TypedConsumerService.SingleMessageConsumeAsync to treat the error as CriticalFailure and call StopApplication, which combined with the unacknowledged message being redelivered on restart results in a permanent crash-loop.