CVE-2025-62842: HBS 3 Path Traversal Vulnerability

CVE-2025-62842 Overview

An external control of file name or path vulnerability (CWE-73) has been identified in QNAP HBS 3 Hybrid Backup Sync. This vulnerability allows an attacker with local network access to exploit the flaw and read or modify files or directories on affected systems. The vulnerability stems from improper handling of external input used in file path operations, which could allow unauthorized access to sensitive data or system modifications.

Critical Impact

Attackers with local network access can exploit this vulnerability to read or modify arbitrary files and directories, potentially leading to data exfiltration, system compromise, or complete loss of data integrity on QNAP NAS devices.

Affected Products

• QNAP HBS 3 Hybrid Backup Sync versions prior to 26.2.0.938

Discovery Timeline

• 2026-01-02 - CVE-2025-62842 published to NVD
• 2026-01-02 - Last updated in NVD database

Technical Details for CVE-2025-62842

Vulnerability Analysis

This vulnerability falls under CWE-73 (External Control of File Name or Path), a class of weaknesses where software allows external parties to control file names or paths used in file operations. In the context of HBS 3 Hybrid Backup Sync, the application fails to properly validate or sanitize user-supplied input that influences file path construction.

When an attacker gains access to the local network where the QNAP device resides, they can craft malicious requests that manipulate file paths. This exploitation technique typically involves path traversal sequences (such as ../) or absolute path injection to escape intended directory boundaries. The consequence is unauthorized read access to sensitive configuration files, credentials, or system data, as well as the ability to modify or delete critical files.

Root Cause

The root cause lies in insufficient input validation for file path parameters within the HBS 3 Hybrid Backup Sync application. The software accepts externally controlled input that is used to construct file system paths without adequate sanitization, allowing attackers to specify arbitrary file locations outside the intended directory scope.

Attack Vector

The attack requires physical or local network access to the target QNAP device. An attacker positioned on the same network segment can send crafted requests to the HBS 3 service that include manipulated file path parameters. These requests bypass intended access restrictions by using path traversal techniques or absolute path specifications to access files or directories outside the application's designated storage areas.

The exploitation does not require authentication, making any HBS 3 instance accessible from the local network potentially vulnerable. Successful exploitation grants the attacker the ability to read sensitive system files, modify configuration data, or manipulate backup data managed by the application.

Detection Methods for CVE-2025-62842

Indicators of Compromise

• Unusual file access patterns in HBS 3 logs showing requests for files outside normal backup directories
• Requests containing path traversal sequences (../, ..\\) in file path parameters
• Unauthorized modifications to system configuration files or backup data
• Access attempts to sensitive directories like /etc/, /root/, or QNAP system paths from the HBS 3 service

Detection Strategies

• Monitor HBS 3 application logs for anomalous file path requests, particularly those containing traversal patterns
• Implement network-level monitoring to detect unusual traffic patterns to the HBS 3 service port
• Deploy file integrity monitoring on critical system files and directories to detect unauthorized changes
• Review authentication logs for failed or suspicious access attempts from unexpected network sources

Monitoring Recommendations

• Enable verbose logging on the HBS 3 Hybrid Backup Sync application
• Configure SIEM rules to alert on path traversal indicators in QNAP device logs
• Implement network segmentation to limit exposure of NAS devices to untrusted network segments
• Regularly audit file access permissions and review backup job configurations for anomalies

How to Mitigate CVE-2025-62842

Immediate Actions Required

• Update HBS 3 Hybrid Backup Sync to version 26.2.0.938 or later immediately
• Restrict network access to QNAP devices to trusted hosts and segments only
• Review system and backup files for signs of unauthorized access or modification
• Enable all available logging features to establish a monitoring baseline

Patch Information

QNAP has released a security update addressing this vulnerability. Users should upgrade to HBS 3 Hybrid Backup Sync version 26.2.0.938 or later. The fix can be obtained through the QNAP App Center or by downloading directly from QNAP's website. For detailed patching instructions, refer to the QNAP Security Advisory QSA-25-46.

Workarounds

• Implement network segmentation to isolate QNAP NAS devices from untrusted network segments
• Configure firewall rules to restrict access to HBS 3 service ports to only authorized management hosts
• Disable the HBS 3 service if not actively in use until patching can be completed
• Enable VPN access requirements for remote administration of QNAP devices