CVE-2025-30187 identifies a vulnerability in PowerDNS DNSdist versions 1.9.0 and 2.0.0 related to the handling of DNS over HTTPS (DoH) queries when the nghttp2 library is used for HTTP/2 processing. Under specific conditions, an attacker can craft a malicious DoH exchange that triggers an infinite loop due to an unreachable exit condition in the code managing I/O reads. This loop causes unbounded CPU consumption, effectively resulting in a denial of service (DoS) by exhausting processing resources on the DNSdist server. The vulnerability is classified under CWE-835, which pertains to loops with unreachable exit conditions, leading to infinite loops. Exploitation does not require any authentication or user interaction but does require network access to the DNSdist service configured for DoH. The CVSS v3.1 base score is 3.7, reflecting low severity primarily because the impact is limited to availability with no confidentiality or integrity compromise, and the attack complexity is high due to the need for specific conditions to trigger the loop. No public exploits or active exploitation have been reported to date. The vulnerability highlights a risk in the integration between DNSdist and the nghttp2 library, emphasizing the importance of robust input handling in protocol implementations. As DNSdist is often deployed in DNS infrastructure to load balance and secure DNS queries, this vulnerability could disrupt DNS resolution services if exploited.

For European organizations, the primary impact of CVE-2025-30187 is the potential disruption of DNS services due to denial of service caused by excessive CPU consumption on DNSdist servers handling DoH queries. This can lead to degraded network performance, increased latency, or complete unavailability of DNS resolution, affecting internal and external communications. Organizations relying on DNSdist for critical DNS infrastructure, especially those supporting DoH to enhance privacy and security, may experience service interruptions impacting business operations, customer access, and online services. While the vulnerability does not expose sensitive data or allow unauthorized changes, the availability impact can indirectly affect confidentiality and integrity by disrupting security monitoring and response capabilities. The low CVSS score reflects limited direct damage, but in high-demand environments or where DNSdist is a single point of failure, the operational impact could be significant. European sectors such as telecommunications, finance, and government, which depend heavily on reliable DNS infrastructure, could be particularly sensitive to such disruptions.

To mitigate CVE-2025-30187, European organizations should prioritize the following actions: 1) Monitor PowerDNS announcements and apply official patches or updates for DNSdist as soon as they are released to address this vulnerability. 2) If immediate patching is not feasible, consider disabling DNS over HTTPS (DoH) processing via the nghttp2 library in DNSdist configurations to prevent triggering the infinite loop. 3) Implement network-level protections such as rate limiting and filtering to restrict suspicious or malformed DoH traffic that could exploit this vulnerability. 4) Deploy robust monitoring of DNSdist CPU usage and query patterns to detect abnormal resource consumption indicative of an attack. 5) Use redundant DNS infrastructure and load balancing to minimize the impact of any single server being affected by a DoS condition. 6) Conduct regular security assessments and penetration testing focusing on DNS services to identify and remediate similar issues proactively. 7) Engage with vendors and security communities to stay informed about emerging threats related to DNSdist and DoH implementations.