CVE-2025-52867 is a medium-severity vulnerability affecting QNAP Systems Inc.'s Qsync Central product, specifically version 5.0.0. This vulnerability is classified under CWE-400, which corresponds to uncontrolled resource consumption, commonly leading to denial-of-service (DoS) conditions. The vulnerability allows a remote attacker who has already obtained a user account on the affected system to exploit the resource consumption flaw to launch a DoS attack. The attack vector is network-based (AV:N), requires low attack complexity (AC:L), and requires privileges (PR:L) but no user interaction (UI:N). The vulnerability does not affect confidentiality, integrity, or availability directly in terms of data compromise but impacts availability by exhausting system resources. The vendor has addressed this issue in Qsync Central version 5.0.0.2 released on July 31, 2025. There are no known exploits in the wild at the time of publication. The vulnerability does not require user interaction but does require the attacker to have a valid user account, which implies some level of prior access or credential compromise. The CVSS 4.0 vector indicates a high impact on availability (VA:H) but no impact on confidentiality or integrity. The vulnerability is significant because Qsync Central is a synchronization and file-sharing service used in QNAP NAS devices, which are widely deployed in enterprise and SMB environments for data storage and collaboration. Exploiting this vulnerability could disrupt business operations by causing service outages or degraded performance due to resource exhaustion.

For European organizations using QNAP NAS devices with Qsync Central version 5.0.0, this vulnerability poses a risk of denial-of-service attacks that could disrupt file synchronization and access services critical to business continuity. The requirement for an attacker to have a user account means that organizations with weak credential management or exposed user accounts are at higher risk. The DoS condition could lead to downtime, impacting productivity and potentially causing data synchronization delays or failures. In sectors such as finance, healthcare, manufacturing, and government, where data availability is crucial, such disruptions could have operational and reputational consequences. Additionally, organizations relying on Qsync Central for remote collaboration may experience interruptions, especially relevant given the increase in remote work across Europe. Although no known exploits are currently reported, the medium severity and ease of exploitation with valid credentials necessitate proactive mitigation to prevent potential attacks.

European organizations should immediately verify the version of Qsync Central running on their QNAP NAS devices and upgrade to version 5.0.0.2 or later, where the vulnerability is fixed. Since exploitation requires a valid user account, organizations must enforce strong credential policies, including complex passwords, regular password changes, and multi-factor authentication (MFA) where supported. Monitoring and auditing user account activity for suspicious logins or unusual behavior can help detect potential compromise early. Network segmentation and limiting access to Qsync Central services to trusted networks or VPNs can reduce exposure. Implementing rate limiting or resource usage monitoring on NAS devices may help detect or mitigate resource exhaustion attempts. Regularly reviewing and removing inactive or unnecessary user accounts will reduce the attack surface. Finally, organizations should stay informed about any emerging exploits or patches related to this vulnerability and apply security updates promptly.