CVE-2025-47711 is a medium severity off-by-one error vulnerability found in the nbdkit server component of Red Hat Enterprise Linux 10, specifically affecting versions 1.11.10, 1.40.0, and 1.42.0. The flaw arises during the handling of responses from nbdkit plugins concerning the status of data blocks. When a client issues a request for an extremely large data range, and the plugin responds with a single data block even larger than requested, the nbdkit server encounters an off-by-one error that triggers a critical internal failure. This failure results in a denial-of-service (DoS) condition, disrupting the availability of the nbdkit service. The vulnerability requires the attacker to have network access and low privileges on the system but does not require user interaction, making it relatively easier to exploit in environments where nbdkit is exposed. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) indicates network attack vector, low attack complexity, privileges required, no user interaction, unchanged scope, no impact on confidentiality or integrity, but high impact on availability. No known exploits have been reported in the wild as of the publication date. The vulnerability is relevant for environments using nbdkit for network block device serving, commonly in virtualization and cloud infrastructure scenarios. Since nbdkit is a plugin-based server, the issue specifically arises from improper handling of plugin responses, indicating a need for careful validation of data block sizes. The flaw is assigned by Red Hat and published in June 2025, with no patch links currently available, suggesting that mitigation efforts should focus on monitoring and limiting exposure until patches are released.

For European organizations, the primary impact of CVE-2025-47711 is the potential for denial-of-service attacks against systems running nbdkit on Red Hat Enterprise Linux 10. This can disrupt critical services relying on network block devices, such as virtualization hosts, cloud infrastructure, and storage services. The availability impact could lead to downtime, affecting business continuity and operational efficiency. Since the vulnerability does not affect confidentiality or integrity, data breaches or manipulation are not direct concerns. However, service outages in sectors like finance, healthcare, telecommunications, and government could have cascading effects on dependent systems and services. Organizations with exposed nbdkit services or those that allow untrusted clients to interact with nbdkit plugins are at higher risk. The requirement for low privileges and network access means internal threat actors or compromised users could exploit this vulnerability, emphasizing the need for strict access controls. The absence of known exploits in the wild provides a window for proactive mitigation but also means organizations should remain vigilant for emerging threats targeting this flaw.

European organizations should implement the following specific mitigations: 1) Restrict network access to nbdkit services by applying firewall rules and network segmentation to limit exposure only to trusted clients. 2) Enforce strict access controls and monitor user privileges to reduce the risk of low-privilege attackers exploiting the vulnerability. 3) Monitor nbdkit logs and system behavior for signs of abnormal requests or service crashes indicative of exploitation attempts. 4) Temporarily disable or limit the use of plugins that handle large data ranges if feasible until patches are available. 5) Engage with Red Hat support and subscribe to security advisories to obtain and apply patches promptly once released. 6) Conduct internal audits to identify all systems running affected nbdkit versions and prioritize remediation. 7) Implement redundancy and failover mechanisms for critical services relying on nbdkit to minimize downtime impact. 8) Consider deploying intrusion detection systems with signatures or heuristics targeting anomalous nbdkit traffic patterns. These steps go beyond generic advice by focusing on access restriction, monitoring, and operational continuity tailored to the nature of this vulnerability.