CVE-2025-29900 is a high-severity vulnerability identified in QNAP Systems Inc.'s File Station 5, specifically affecting versions 5.5.x prior to 5.5.6.4907. The vulnerability is classified under CWE-770, which pertains to the allocation of resources without limits or throttling. In this case, a remote attacker who has obtained a user account on the affected system can exploit this flaw to exhaust certain system resources. This resource exhaustion prevents other systems, applications, or processes from accessing the same type of resource, effectively causing a denial of service (DoS) condition. The vulnerability does not require user interaction and can be exploited remotely with low attack complexity, as no additional authentication beyond a user account is necessary. The CVSS 4.0 base score is 7.1, reflecting a high severity due to the potential for significant impact on availability (VA:H) without affecting confidentiality or integrity. The vulnerability has been addressed in File Station 5 version 5.5.6.4907 and later, indicating that patching is available. No known exploits are currently reported in the wild, but the risk remains due to the ease of exploitation once an attacker has user credentials. The vulnerability's root cause is the lack of resource allocation limits or throttling, which allows an attacker to monopolize resources, leading to service disruption for legitimate users or dependent processes.

For European organizations using QNAP NAS devices with File Station 5, this vulnerability poses a significant risk to service availability. Many enterprises, SMBs, and public sector entities in Europe rely on QNAP NAS for file sharing, backup, and collaboration. Exploitation could lead to denial of service conditions, disrupting business operations, data access, and potentially impacting critical workflows. This is particularly concerning for sectors with high availability requirements such as healthcare, finance, and government services. Additionally, since exploitation requires only a user account, insider threats or compromised credentials could be leveraged to cause disruption. The lack of impact on confidentiality and integrity reduces the risk of data breaches but does not diminish the operational impact. The unavailability of file services could also indirectly affect compliance with data availability regulations under GDPR if critical data access is interrupted. Given the widespread use of QNAP devices in Europe, the operational and reputational impact could be substantial if the vulnerability is exploited at scale.

European organizations should prioritize immediate patching of all affected QNAP File Station 5 installations to version 5.5.6.4907 or later. Beyond patching, organizations should enforce strict user account management policies, including the principle of least privilege, to limit the number of users with access to File Station. Implementing multi-factor authentication (MFA) can reduce the risk of credential compromise. Network segmentation should be used to isolate NAS devices from broader enterprise networks, limiting exposure. Monitoring and alerting for unusual resource consumption or service disruptions on NAS devices can provide early detection of exploitation attempts. Additionally, organizations should review and limit API or service access to File Station where possible, and consider rate limiting or resource throttling at the network or application layer as a compensating control until patches are applied. Regular audits of user accounts and access logs will help identify potential misuse or compromise. Finally, organizations should maintain up-to-date backups to mitigate the impact of service disruptions.