CVE-2026-0398 is a vulnerability identified in PowerDNS Recursor versions 5.1.0, 5.2.0, and 5.3.0, involving improper allocation of resources without adequate limits or throttling mechanisms. This flaw allows an attacker to craft malicious DNS zones that cause the Recursor to consume excessive CPU and memory resources, potentially leading to denial of service (DoS) conditions. Furthermore, the vulnerability includes the possibility of cache poisoning through carefully constructed CNAME chains, which can manipulate DNS cache entries and potentially redirect DNS queries to malicious destinations. The vulnerability is exploitable remotely without requiring authentication or user interaction, increasing its risk profile. However, the impact on confidentiality and integrity is minimal, as the primary effect is on availability through resource exhaustion. The CVSS 3.1 base score is 5.3, indicating medium severity, with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L. No public exploits have been reported yet, but the vulnerability's nature suggests that attackers could leverage it to disrupt DNS resolution services. PowerDNS Recursor is widely used in DNS infrastructure, including by ISPs and enterprises, making this vulnerability relevant for critical DNS operations.

For European organizations, the primary impact of CVE-2026-0398 is the potential degradation or denial of DNS resolution services due to resource exhaustion. DNS is a foundational service for network operations, and disruption can affect web services, email, and internal applications. Cache poisoning via crafted CNAME chains could lead to redirection of DNS queries to malicious sites, increasing the risk of phishing, malware distribution, or data interception. Organizations relying on PowerDNS Recursor for authoritative or recursive DNS services may experience outages or degraded performance, impacting business continuity and user trust. Critical infrastructure providers, ISPs, and large enterprises with public-facing DNS services are particularly at risk. The absence of authentication requirements and the ability to exploit remotely heighten the threat, especially in environments with high DNS query volumes or exposure to untrusted networks. Although no known exploits exist currently, the vulnerability could be targeted in future attacks, especially in geopolitical contexts where DNS manipulation is a tactic.

Organizations should promptly upgrade PowerDNS Recursor to a patched version once available, as no patch links are currently provided but are expected. In the interim, implement strict DNS query rate limiting and resource usage monitoring to detect and mitigate abnormal spikes caused by crafted zones. Deploy DNS firewalling or filtering to block suspicious or malformed DNS queries, particularly those involving unusual CNAME chains. Use network-level protections such as ingress filtering and anomaly detection to identify potential exploitation attempts. Consider isolating DNS resolvers behind dedicated infrastructure with limited exposure to untrusted networks. Regularly audit DNS configurations and logs for signs of cache poisoning or resource abuse. Collaborate with DNS service providers and security vendors to stay informed about updates and emerging threats related to this vulnerability. Finally, incorporate DNS security extensions (DNSSEC) where possible to reduce the risk of cache poisoning attacks.