CVE-2026-73798 in NonStop DNS
Summary
by MITRE • 10/14/2026
A security vulnerability in HPE NonStop DNS 9.2.3 Non Secure Version could cause a Denial of Service.
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Analysis
by VulDB Data Team • 10/14/2026
The HPE NonStop DNS software, specifically version 9.2.3 running the non-secure variant, contains a critical flaw that can be exploited to trigger a denial of service condition within the domain name system infrastructure. This vulnerability stems from an improper handling of specific network requests or malformed data packets directed at the DNS resolver services hosted on these systems. In enterprise environments utilizing HPE NonStop servers for high availability and transaction processing, the DNS layer serves as a foundational component for internal communication and external resolution. When the service encounters input that violates expected protocol constraints or triggers an unhandled exception in its parsing logic, it fails to recover gracefully, leading to a crash of the DNS process or a complete halt of name resolution capabilities across the affected host.
From a technical perspective, this issue aligns with common weaknesses found in legacy network services where robust error handling and input validation are insufficient against crafted malicious payloads. The vulnerability likely involves a buffer overflow, integer overflow, or resource exhaustion scenario that depletes system memory or CPU resources beyond acceptable thresholds. Because the affected version is explicitly noted as non-secure, it may lack modern cryptographic protections or hardened security configurations, making it more susceptible to exploitation by attackers who can send specially crafted UDP packets designed to trigger this instability. The absence of secure defaults often means that authentication mechanisms are either weak or nonexistent for certain administrative functions, allowing unauthenticated actors to interact with the service and induce failure states.
The operational impact of such a vulnerability is severe in environments where continuous uptime is paramount. A successful exploitation results in the inability of systems relying on this DNS server to resolve domain names, effectively isolating them from network resources that depend on name resolution. This disruption can cascade into broader application failures, particularly for distributed applications and database clusters that require constant connectivity to remote services or internal microservices. For organizations running HPE NonStop systems, which are often deployed in mission-critical sectors like finance and healthcare, this outage represents a significant risk to business continuity and data integrity during the period of service unavailability.
Mitigation strategies should prioritize immediate isolation of the affected system from untrusted networks if possible, followed by upgrading to a secure version of HPE NonStop DNS that includes patches for this specific flaw. If an upgrade is not immediately feasible, implementing network-level access control lists to restrict UDP traffic to only known and trusted resolvers can reduce the attack surface significantly. Additionally, enabling logging on the firewall or intrusion detection systems to monitor for anomalous query patterns associated with denial of service attacks provides early warning indicators. Organizations must also review their overall DNS architecture to ensure redundancy is in place so that a single point of failure does not compromise the entire network infrastructure.
This vulnerability corresponds to CWE-20, which describes improper input validation, as well as CWE-400 concerning uncontrolled resource consumption leading to denial of service conditions. In terms of adversarial tactics, this aligns with MITRE ATT&CK techniques related to Service Disruption, specifically those involving application layer attacks that target the availability component of the CIA triad. Security teams should treat this issue with high priority due to its direct impact on system availability and the potential for widespread operational disruption in legacy enterprise environments dependent on HPE NonStop infrastructure.