CVE-2025-62850: QNAP QuTS Hero DoS Vulnerability

CVE-2025-62850 Overview

CVE-2025-62850 is a NULL pointer dereference vulnerability [CWE-476] affecting multiple versions of the QNAP QuTS hero operating system. A remote attacker with administrator credentials can trigger the flaw to cause a denial-of-service (DoS) condition on the affected device. QNAP has released fixes in QuTS hero h5.2.9.3410 build 20260214, h5.3.4.3500 build 20260520, and h6.0.0.3459 build 20260409. The vulnerability requires high privileges and network access, limiting the realistic attack surface to environments where administrator credentials may be compromised or shared.

Critical Impact

An authenticated remote administrator can crash affected QNAP QuTS hero services, disrupting storage availability for users and dependent systems.

Affected Products

• QNAP QuTS hero versions prior to h5.2.9.3410 build 20260214
• QNAP QuTS hero versions prior to h5.3.4.3500 build 20260520
• QNAP QuTS hero versions prior to h6.0.0.3459 build 20260409

Discovery Timeline

• 2026-06-10 - CVE-2025-62850 published to NVD
• 2026-06-10 - Last updated in NVD database

Technical Details for CVE-2025-62850

Vulnerability Analysis

The vulnerability is classified as a NULL pointer dereference [CWE-476] in the QNAP QuTS hero operating system. A NULL pointer dereference occurs when code attempts to read or write memory using a pointer that has not been assigned a valid object reference. When triggered, the operating system fault handler terminates the offending process or service, resulting in a denial-of-service condition. The QNAP advisory states that exploitation requires an administrator account on the target device. Successful exploitation does not result in code execution, privilege escalation, or data disclosure based on the vendor advisory.

Root Cause

The underlying defect stems from missing validation of a pointer before it is dereferenced inside an affected QuTS hero component. QNAP has not published source-level details about the specific subsystem involved. The flaw is reachable through an authenticated network-facing administrative interface exposed by the NAS operating system.

Attack Vector

Exploitation requires network access to the QuTS hero management interface and valid administrator credentials. After authentication, the attacker submits crafted input to the vulnerable code path, causing the affected service or process to dereference a NULL pointer and terminate. Because no user interaction is required and the attack vector is network-based, automation against exposed appliances with weak or stolen administrator credentials is feasible. Refer to the QNAP Security Advisory QSA-26-38 for vendor-supplied technical details.

Detection Methods for CVE-2025-62850

Indicators of Compromise

• Unexpected restarts or crashes of QuTS hero services or daemons logged in /var/log/ on the appliance.
• Repeated failed or successful administrator authentication events from unfamiliar source IP addresses immediately preceding service failure.
• Loss of NAS-hosted shares, iSCSI targets, or management UI availability without scheduled maintenance.

Detection Strategies

• Monitor QuTS hero system event logs for service crash entries correlated with administrator session activity.
• Alert on administrator logins to QNAP devices from outside expected management networks or geographies.
• Track the running firmware build on each appliance and flag any device that has not been updated to a fixed build.

Monitoring Recommendations

• Forward QNAP syslog output to a centralized logging or SIEM platform for retention and correlation with identity events.
• Baseline normal administrator activity, including source IPs, session times, and configuration changes, and alert on deviations.
• Continuously check appliance availability with synthetic health probes so DoS conditions are detected within minutes.

How to Mitigate CVE-2025-62850

Immediate Actions Required

• Upgrade affected appliances to QuTS hero h5.2.9.3410 build 20260214, h5.3.4.3500 build 20260520, or h6.0.0.3459 build 20260409 or later.
• Restrict access to the QNAP management interface so it is reachable only from trusted administrative networks.
• Rotate administrator credentials and enforce multi-factor authentication on all QNAP administrator accounts.

Patch Information

QNAP has released fixes in QuTS hero h5.2.9.3410 build 20260214, h5.3.4.3500 build 20260520, and h6.0.0.3459 build 20260409. Apply the corresponding build for the version branch deployed in your environment. See the QNAP Security Advisory QSA-26-38 for vendor guidance and download links.

Workarounds

• Limit administrator account membership to the minimum required personnel and audit existing accounts for unused or shared logins.
• Place QNAP appliances behind a VPN or jump host so the management interface is not exposed to untrusted networks.
• Enable account lockout and IP block policies in the QNAP security settings to slow credential-based attacks against administrator accounts.

# Verify the running QuTS hero version on the appliance
getcfg System Version -f /etc/config/uLinux.conf
getcfg System "Build Number" -f /etc/config/uLinux.conf