In Lightbend Akka before 2.8.1, the async-dns resolver (used by Discovery in DNS mode and transitively by Cluster Bootstrap) uses predictable DNS transaction IDs when resolving DNS records, making DNS resolution subject to poisoning by an attacker. If the application performing discovery does not validate (e.g., via TLS) the authenticity of the discovered service, this may result in exfiltration of application data (e.g., persistence events may be published to an unintended Kafka broker). If such validation is performed, then the poisoning constitutes a denial of access to the intended service. This affects Akka 2.5.14 through 2.8.0, and Akka Discovery through 2.8.0.