CVE-2023-31442 in Lightbend Akka
Summary
by MITRE • 05/11/2023
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.
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Analysis
by VulDB Data Team • 12/24/2025
The vulnerability CVE-2023-31442 affects Lightbend Akka versions prior to 2.8.1 and represents a significant DNS security flaw that undermines the integrity of service discovery mechanisms. This issue specifically impacts the async-dns resolver component that is integral to Akka's Discovery functionality when operating in DNS mode, as well as the Cluster Bootstrap feature that relies on this discovery mechanism. The vulnerability stems from the predictable nature of DNS transaction IDs used during DNS resolution processes, creating an exploitable condition that allows attackers to perform DNS cache poisoning attacks against affected systems.
The technical flaw lies in the implementation of the DNS resolver where the transaction IDs used for DNS queries are not properly randomized or seeded with sufficient entropy. According to CWE-310, this represents a weakness in cryptographic randomness or entropy sources that leads to predictable values. The predictable transaction IDs enable an attacker positioned within the network to intercept DNS responses and inject malicious records into the DNS cache, effectively redirecting service discovery requests to attacker-controlled endpoints. This vulnerability operates at the network layer and affects the fundamental trust model of distributed systems relying on DNS-based service discovery.
The operational impact of this vulnerability extends beyond simple service disruption to encompass data exfiltration and system compromise scenarios. When applications rely on DNS discovery without additional authentication mechanisms such as TLS validation, the poisoned DNS responses can redirect critical operations to malicious endpoints, potentially leading to data leakage or unauthorized access to backend services. For instance, if persistence events are published to Kafka brokers, an attacker could redirect these events to their own infrastructure, enabling data exfiltration and potential system compromise. Even when TLS validation is implemented, the poisoning attack still results in denial of service by preventing legitimate access to intended services, effectively blocking legitimate system operations.
Mitigation strategies for this vulnerability require immediate patching of affected Akka versions to 2.8.1 or later, which addresses the predictable transaction ID issue through proper randomization of DNS transaction identifiers. Organizations should also implement additional network-level protections such as DNS security extensions (DNSSEC) to provide cryptographic authentication of DNS responses, though this requires broader infrastructure support. Network segmentation and monitoring should be enhanced to detect anomalous DNS traffic patterns that might indicate poisoning attempts. The ATT&CK framework categorizes this vulnerability under T1071.004 for DNS tunneling and T1566 for credential access through social engineering, though the specific technique here involves network-level manipulation rather than social engineering. Additionally, implementing proper service validation mechanisms beyond DNS resolution, such as certificate pinning or service identity verification, provides defense-in-depth against this class of attacks.