CVE-2025-59029 is a vulnerability identified in PowerDNS Recursor version 5.3.0, categorized under CWE-617 (Reachable Assertion). The flaw allows an attacker to remotely trigger an assertion failure within the DNS resolver by first sending crafted DNS records that are inserted into the resolver's cache. Subsequently, the attacker issues a DNS query with the query type (qtype) set to ANY. This sequence causes the software to hit an assertion that is reachable during normal operation, resulting in a crash of the DNS recursor process. The vulnerability is exploitable over the network without requiring authentication or user interaction, making it accessible to any remote attacker. The impact is limited to availability, as the assertion failure causes a denial of service (DoS) by crashing the DNS resolver, potentially disrupting DNS resolution services for clients relying on the affected server. The CVSS v3.1 base score is 5.3, reflecting a medium severity level due to the lack of impact on confidentiality or integrity and the absence of privilege requirements. No patches or fixes have been published yet, and no active exploitation has been reported. This vulnerability highlights the importance of robust input validation and error handling in DNS software to prevent assertion failures that can be triggered by malformed queries or cached data.

For European organizations, the primary impact of CVE-2025-59029 is the potential for denial of service against DNS infrastructure relying on PowerDNS Recursor 5.3.0. DNS is a critical service for network operations, and disruption can lead to loss of access to internal and external resources, impacting business continuity and user productivity. Organizations operating public-facing DNS resolvers or internal recursive resolvers using the affected version are at risk of service outages. This can affect ISPs, hosting providers, enterprises, and government agencies. Given the medium severity and lack of confidentiality or integrity impact, the threat is mainly operational. However, DNS outages can cascade into broader service disruptions, affecting web services, email, and other dependent applications. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially if attackers develop exploit code. European entities with critical infrastructure or high dependency on DNS services should prioritize mitigation to maintain service availability.

1. Monitor PowerDNS official channels for patches or updates addressing CVE-2025-59029 and apply them promptly once available. 2. If immediate patching is not possible, consider deploying network-level protections such as rate limiting or filtering DNS queries with qtype ANY from untrusted sources to reduce the attack surface. 3. Implement DNS query logging and anomaly detection to identify unusual patterns indicative of exploitation attempts involving crafted records or ANY queries. 4. Use DNS firewalling or response policy zones (RPZ) to block or redirect suspicious queries. 5. Deploy redundant DNS resolvers with diverse software stacks to ensure continuity if one resolver is affected. 6. Regularly audit and update DNS infrastructure configurations to minimize exposure. 7. Educate network operations teams on this vulnerability to enable rapid response to potential incidents. 8. Consider isolating recursive DNS resolvers from direct internet exposure where feasible, restricting access to trusted clients only.