CVE-2025-30271 is a path traversal vulnerability (CWE-22) affecting QNAP Systems Inc.'s QTS operating system, specifically versions 5.2.x prior to 5.2.5.3145 build 20250526 and QuTS hero h5.2.5.3138 build 20250519. The vulnerability allows an authenticated remote attacker—who has already obtained a user-level account—to exploit the flaw to read arbitrary files on the system outside the intended directory scope. Path traversal vulnerabilities occur when user-supplied input is insufficiently sanitized, enabling attackers to manipulate file paths to access unauthorized files or directories. In this case, the attacker can leverage this to read sensitive system files or data that should otherwise be inaccessible. The vulnerability has a CVSS 4.0 base score of 5.3, indicating a medium severity level. The vector metrics specify network attack vector (AV:N), low attack complexity (AC:L), no privileges required beyond user-level (PR:L), no user interaction (UI:N), and limited confidentiality impact (VC:L) with no impact on integrity or availability. No known exploits are currently reported in the wild, and the vendor has released patches addressing the issue in the specified versions. This vulnerability is significant because QNAP NAS devices are widely used for data storage and sharing in enterprise and SMB environments, and unauthorized file disclosure could lead to leakage of sensitive information or facilitate further attacks.

For European organizations using QNAP NAS devices running vulnerable QTS versions, this vulnerability poses a risk of unauthorized disclosure of sensitive files, including configuration files, credentials, or business-critical data stored on the NAS. Since the attacker requires only a valid user account, compromised or weak credentials could be leveraged to exploit this flaw. The impact includes potential data breaches, violation of data protection regulations such as GDPR, and exposure of intellectual property. Additionally, attackers could use the disclosed information to escalate privileges or pivot within the network, increasing the risk of broader compromise. The medium severity rating reflects the limited scope of impact (confidentiality only) and the prerequisite of user-level access, but the widespread use of QNAP devices in European enterprises and SMBs amplifies the threat. Organizations in sectors with strict compliance requirements or handling sensitive personal data are particularly at risk.

European organizations should immediately verify their QNAP NAS firmware versions and upgrade to QTS 5.2.5.3145 build 20250526 or later, or QuTS hero h5.2.5.3138 build 20250519 or later, as provided by the vendor. Beyond patching, organizations must enforce strong authentication policies, including multi-factor authentication (MFA) for all user accounts accessing NAS devices to reduce the risk of credential compromise. Regularly audit user accounts and permissions to ensure least privilege principles are applied, removing or disabling unnecessary accounts. Network segmentation should be implemented to restrict NAS device access to trusted internal networks or VPNs, minimizing exposure to remote attackers. Monitoring and logging access to NAS devices should be enhanced to detect unusual file access patterns indicative of exploitation attempts. Finally, organizations should conduct regular vulnerability assessments and penetration testing focused on NAS devices to proactively identify and remediate security weaknesses.