CVE-2025-29901 is a high-severity vulnerability identified in QNAP Systems Inc.'s File Station 5, specifically affecting versions 5.5.x prior to 5.5.6.4933. The vulnerability is classified as a NULL pointer dereference (CWE-476), which occurs when the software attempts to access or dereference a pointer that has a null value, leading to an unexpected program crash or denial of service (DoS). In this case, the flaw allows a remote attacker who has already obtained a valid user account on the affected system to exploit the vulnerability and cause a denial-of-service condition, effectively disrupting the availability of the File Station service. The CVSS 4.0 base score is 7.1, indicating a high severity level, with the vector string AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N. This means the attack can be performed remotely over the network with low attack complexity, requires no user interaction, but does require privileges of a legitimate user (PR:L). The vulnerability impacts availability significantly (VA:H), while confidentiality and integrity remain unaffected. No known exploits are reported in the wild as of the publication date (August 26, 2025). The vendor has addressed the issue in File Station 5 version 5.5.6.4933 and later, recommending immediate patching to mitigate the risk. The vulnerability does not require user interaction and does not involve scope changes or security bypass, focusing primarily on availability disruption through a denial-of-service attack.

For European organizations using QNAP NAS devices with File Station 5, this vulnerability poses a significant risk to service availability. File Station is commonly used for file management and sharing within enterprise and SMB environments, and a denial-of-service attack could disrupt critical business operations, data access, and collaboration workflows. Since exploitation requires a valid user account, the threat is particularly relevant in environments where user credentials may be compromised or where insider threats exist. The disruption could affect sectors relying on continuous access to shared storage, such as finance, healthcare, education, and public administration. Additionally, prolonged denial-of-service conditions could lead to operational downtime, loss of productivity, and potential reputational damage. Although confidentiality and integrity are not directly impacted, the availability impact alone can have cascading effects on business continuity and compliance with data availability regulations under GDPR and other European frameworks.

European organizations should prioritize upgrading File Station 5 to version 5.5.6.4933 or later to remediate this vulnerability. Beyond patching, organizations should implement strict access controls and monitoring to limit the risk of credential compromise, including enforcing strong authentication mechanisms such as multi-factor authentication (MFA) for all user accounts accessing QNAP devices. Network segmentation should be employed to isolate NAS devices from broader enterprise networks, reducing the attack surface. Regular auditing of user accounts and permissions can help detect and remove unnecessary or dormant accounts that could be leveraged by attackers. Additionally, deploying anomaly detection systems to monitor unusual access patterns or service disruptions on NAS devices can provide early warning of exploitation attempts. Organizations should also maintain up-to-date backups to ensure data availability in case of service disruption and incorporate incident response plans specific to NAS device outages.