CVE-2025-62855: QNAP File Station Path Traversal Flaw

CVE-2025-62855 Overview

A path traversal vulnerability has been identified in QNAP File Station 5, a file management application for QNAP NAS devices. This vulnerability allows a local attacker who has already gained administrator account access to exploit the flaw and read the contents of unexpected files or system data beyond the intended directory scope.

Critical Impact

Authenticated administrators can exploit this path traversal vulnerability to access sensitive files and system data outside of intended directories, potentially exposing configuration files, credentials, or other sensitive information stored on the NAS device.

Affected Products

• QNAP File Station 5 versions prior to 5.5.6.5190
• QNAP NAS devices running vulnerable File Station 5 installations

Discovery Timeline

• 2026-02-11 - CVE-2025-62855 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2025-62855

Vulnerability Analysis

This vulnerability is classified as CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal. The flaw exists within File Station 5's file handling mechanisms, where insufficient validation of user-supplied file paths allows attackers to escape the intended directory structure.

The attack requires the adversary to first obtain administrator-level credentials for the QNAP device. Once authenticated, they can craft malicious requests containing directory traversal sequences (such as ../) to access files outside the designated file system boundaries. This could expose sensitive system configuration files, user data, or other protected resources stored on the NAS.

While the severity is rated as low due to the prerequisite of having administrator access, the vulnerability remains significant in environments where administrator credentials may be shared, compromised through other means, or in scenarios involving insider threats.

Root Cause

The root cause of this vulnerability lies in improper input validation within File Station 5's path handling logic. The application fails to adequately sanitize or canonicalize file path inputs before processing file read operations, allowing directory traversal sequences to be interpreted and executed.

Attack Vector

The attack is network-accessible and requires the attacker to have valid administrator credentials for the QNAP device. The exploitation flow involves:

1. The attacker authenticates to the QNAP device with administrator privileges
2. Through File Station 5's interface or API, the attacker submits a crafted request containing path traversal sequences
3. The vulnerable application processes the malicious path without proper sanitization
4. The attacker gains access to files outside the intended directory, potentially reading sensitive system data or configuration files

The attack complexity is low, requiring no user interaction beyond the initial authentication.

Detection Methods for CVE-2025-62855

Indicators of Compromise

• Unusual file access patterns in File Station 5 logs showing requests with ../ or encoded traversal sequences
• Administrator account activity accessing system files outside normal File Station directories
• Log entries indicating access to sensitive configuration files like /etc/passwd or QNAP system configuration files

Detection Strategies

• Monitor File Station 5 access logs for requests containing directory traversal patterns such as ../, ..%2f, or ..%5c
• Implement alerting on administrator account activity that accesses files outside typical user data directories
• Deploy file integrity monitoring on sensitive system files to detect unauthorized reads
• Review authentication logs for unusual administrator login patterns or credential usage

Monitoring Recommendations

• Enable comprehensive logging for File Station 5 file operations and API requests
• Configure SIEM rules to detect path traversal patterns in web server and application logs
• Monitor for access to system-sensitive directories from File Station processes
• Implement baseline alerts for administrator account file access behavior anomalies

How to Mitigate CVE-2025-62855

Immediate Actions Required

• Update QNAP File Station 5 to version 5.5.6.5190 or later immediately
• Review administrator account access and remove unnecessary privileged accounts
• Audit recent File Station 5 activity logs for signs of exploitation
• Implement strong authentication measures including multi-factor authentication for administrator accounts

Patch Information

QNAP has released a security update addressing this vulnerability. File Station 5 version 5.5.6.5190 and later versions contain the fix for CVE-2025-62855. Users should update through the QNAP App Center or download the update directly from the QNAP Security Advisory QSA-26-03.

Workarounds

• Restrict administrator account access to only essential personnel
• Implement network segmentation to limit access to QNAP management interfaces
• Enable and review audit logging for all administrator activities
• Consider disabling File Station 5 temporarily if immediate patching is not possible and the feature is not critical

# Configuration example - Verify File Station version after update
cat /home/httpd/cgi-bin/filemanager/utilRequest.cgi | grep -i version
# Ensure version shows 5.5.6.5190 or later

# Review recent file access logs for suspicious patterns
grep -E "\.\./|%2e%2e" /var/log/filestation.log