CVE-2025-52865 Overview
CVE-2025-52865 is a NULL pointer dereference vulnerability [CWE-476] in QNAP File Station 5. An authenticated remote attacker with a valid user account can trigger the flaw to cause a denial-of-service (DoS) condition on the affected service. The issue is tracked in QNAP Security Advisory QSA-25-38 and has been resolved in File Station 5 version 5.5.6.5018 and later.
Critical Impact
Authenticated remote attackers can disrupt File Station 5 availability by triggering a NULL pointer dereference, resulting in a denial-of-service condition on the QNAP service.
Affected Products
- QNAP File Station 5 (versions prior to 5.5.6.5018)
- QNAP NAS devices running vulnerable File Station 5 builds
- Deployments exposing File Station 5 to authenticated remote users
Discovery Timeline
- 2025-11-07 - CVE-2025-52865 published to the National Vulnerability Database (NVD)
- 2026-10-18 - Last updated in NVD database
Technical Details for CVE-2025-52865
Vulnerability Analysis
The flaw resides in QNAP File Station 5, a web-based file management application for QNAP NAS appliances. The vulnerability is classified as a NULL pointer dereference [CWE-476]. When the vulnerable code path is reached, the application attempts to read or write memory through a pointer that has not been assigned a valid address. This causes the handling process or thread to terminate abnormally, interrupting File Station services for legitimate users.
Exploitation requires an authenticated session, so the attacker must already possess valid credentials for the target NAS. The impact is limited to availability. Confidentiality and integrity are not affected, as no data is disclosed or modified by the condition itself.
Root Cause
The root cause is missing validation of a pointer before dereferencing it in a request-handling routine within File Station 5. Vendor documentation in QNAP Security Advisory QSA-25-38 confirms the fix is delivered in File Station 5 build 5.5.6.5018, which adds the required pointer checks.
Attack Vector
The attack vector is network based. An attacker with a low-privileged account sends a crafted request to the File Station 5 endpoint over HTTP or HTTPS. The malformed request steers execution into the vulnerable code path, dereferencing an uninitialized or NULL pointer and crashing the handling process. No user interaction is required beyond the attacker's own authenticated request.
No public proof-of-concept or exploit code is available for this issue at the time of writing. Refer to the QNAP advisory for vendor-authored technical details.
Detection Methods for CVE-2025-52865
Indicators of Compromise
- Unexpected crashes or restarts of File Station 5 processes on QNAP NAS devices
- Repeated HTTP or HTTPS requests to File Station 5 endpoints from a single authenticated session followed by service interruption
- Elevated error entries in QNAP system logs tied to File Station request handling
Detection Strategies
- Monitor QNAP system and application logs for abnormal termination of File Station 5 and associated worker processes
- Correlate authentication events with service availability alerts to identify authenticated users triggering repeated crashes
- Baseline normal File Station 5 request patterns and alert on anomalous request bodies or parameters from low-privileged accounts
Monitoring Recommendations
- Collect QNAP NAS logs centrally and retain them for post-incident analysis of DoS activity
- Alert on File Station service downtime or restart loops that coincide with recent authenticated access
- Track failed and successful logins to File Station 5 to detect account compromise that could enable this attack
How to Mitigate CVE-2025-52865
Immediate Actions Required
- Upgrade File Station 5 to version 5.5.6.5018 or later on all QNAP NAS devices
- Review File Station 5 user accounts and remove or disable unused or stale credentials
- Restrict File Station 5 exposure to trusted networks until patching is complete
Patch Information
QNAP has published the fix in File Station 5 build 5.5.6.5018 and later. Administrators should apply the update through the QNAP App Center or follow the guidance in QNAP Security Advisory QSA-25-38. After updating, verify the installed version in the App Center to confirm remediation.
Workarounds
- Limit File Station 5 access to trusted IP ranges using the QNAP firewall or an upstream network ACL
- Enforce strong authentication, including two-factor authentication, to reduce the risk of credential-based access
- Temporarily disable File Station 5 on exposed NAS devices if immediate patching is not possible
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
