CVE-2025-62840 is a vulnerability identified in QNAP Systems Inc.'s HBS 3 Hybrid Backup Sync software, specifically affecting version 26.1.x. The flaw is categorized under CWE-209, which involves the generation of error messages that expose sensitive information. In this case, the application improperly handles error conditions, resulting in error messages that leak application data which could include configuration details, user information, or other sensitive internal states. The vulnerability requires the attacker to have local network access, meaning they must be on the same network segment or have equivalent access to the device's network interface. No authentication or user interaction is required to exploit this vulnerability, making it easier for an attacker with local access to leverage it. The CVSS 4.0 vector indicates the attack vector is physical or local network (AV:P), with low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact metrics show high confidentiality (VC:H), integrity (VI:H), and availability (VA:H) impacts, suggesting that exploitation could lead to significant data exposure and potentially disrupt backup synchronization processes. The vulnerability was publicly disclosed on January 2, 2026, and has been addressed in HBS 3 version 26.2.0.938 and later. There are no known exploits in the wild at this time, but the presence of sensitive data exposure in error messages poses a risk of information leakage that could facilitate further attacks. The vulnerability affects organizations using QNAP NAS devices running the vulnerable HBS 3 software, particularly in environments where local network access is not tightly controlled.

For European organizations, the impact of CVE-2025-62840 can be significant, especially for those relying on QNAP NAS devices for backup and synchronization tasks. Exposure of sensitive application data through error messages can lead to unauthorized disclosure of configuration details, user credentials, or other critical information. This leakage can facilitate lateral movement within the network, privilege escalation, or targeted attacks against backup infrastructure. The high impact on confidentiality, integrity, and availability means that data backups could be compromised or manipulated, potentially leading to data loss or corruption. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, which often use NAS devices for data storage and backup, are particularly at risk. Additionally, the requirement for local network access means that internal threat actors or attackers who have breached perimeter defenses could exploit this vulnerability to gain further foothold. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits following public disclosure. Therefore, European organizations must prioritize patching and network access controls to mitigate potential damage.

1. Upgrade QNAP HBS 3 Hybrid Backup Sync to version 26.2.0.938 or later immediately to apply the official patch addressing CVE-2025-62840. 2. Implement strict network segmentation to limit local network access to NAS devices only to trusted and authorized users and systems. 3. Employ network access control (NAC) solutions to enforce device authentication and restrict unauthorized devices from connecting to the local network. 4. Monitor network traffic to and from NAS devices for unusual access patterns or error message leakage that could indicate exploitation attempts. 5. Disable or restrict unnecessary services on QNAP devices to reduce the attack surface. 6. Conduct regular security audits and vulnerability scans on NAS devices to detect outdated software versions or misconfigurations. 7. Educate internal users about the risks of local network threats and enforce strong internal security policies to prevent insider threats. 8. Consider deploying intrusion detection/prevention systems (IDS/IPS) that can detect anomalous behavior related to backup synchronization processes.