CVE-2025-62842 is a vulnerability classified under CWE-73 (External Control of File Name or Path) affecting QNAP Systems Inc.'s HBS 3 Hybrid Backup Sync software, specifically versions 26.1.x. This vulnerability allows an attacker who has gained access to the local network to manipulate file names or paths processed by the software, enabling unauthorized reading or modification of files and directories. The vulnerability does not require authentication or user interaction, which increases its exploitability within a local network environment. The CVSS 4.0 base score is 7.0, indicating a high severity level, with attack vector being local network (AV:P), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact metrics indicate high confidentiality, integrity, and availability impacts (C:H, I:H, A:H), meaning the attacker can fully compromise data confidentiality, alter data integrity, and disrupt availability of files managed by the backup sync software. The vulnerability was reserved in October 2025 and published in January 2026. The vendor has addressed the issue in version 26.2.0.938 and later. No known exploits have been reported in the wild yet, but the nature of the vulnerability and ease of exploitation make it a significant risk for organizations using vulnerable QNAP NAS devices. The vulnerability could be leveraged to compromise backup data, potentially leading to data loss, ransomware deployment, or lateral movement within networks.

For European organizations, the impact of CVE-2025-62842 is substantial, especially for those relying on QNAP NAS devices with HBS 3 Hybrid Backup Sync for critical data backup and synchronization. Successful exploitation can lead to unauthorized disclosure of sensitive data, tampering with backup files, or disruption of backup operations, which can severely affect business continuity and data integrity. Industries such as finance, healthcare, manufacturing, and public sector entities that use QNAP devices for data storage and backup are particularly at risk. The ability to exploit this vulnerability without authentication or user interaction lowers the barrier for attackers who have local network access, including insider threats or attackers who have compromised less secure network segments. This could facilitate further attacks such as ransomware deployment or data exfiltration. Given the high confidentiality, integrity, and availability impacts, organizations could face regulatory penalties under GDPR if personal data is compromised. The threat also poses risks to operational technology environments that integrate QNAP devices for backup, potentially affecting critical infrastructure.

To mitigate the risk posed by CVE-2025-62842, European organizations should immediately upgrade all affected QNAP HBS 3 Hybrid Backup Sync installations to version 26.2.0.938 or later, where the vulnerability is patched. Network segmentation should be enforced to restrict access to NAS devices only to trusted and necessary hosts, minimizing exposure to local network attackers. Implement strict access controls and monitoring on network segments hosting QNAP devices to detect unauthorized access attempts. Employ network intrusion detection systems (NIDS) to identify suspicious activities targeting NAS devices. Regularly audit backup data integrity and access logs to detect potential tampering. Disable any unnecessary services on QNAP devices to reduce the attack surface. Additionally, organizations should educate internal users about the risks of local network threats and enforce strong internal network security policies. Backup data should be encrypted and stored in multiple locations to ensure availability in case of compromise. Finally, maintain up-to-date firmware and software versions on all network-attached storage devices and related infrastructure.