Source: security@qnapsecurity.com.tw
A vulnerability has been reported to affect earlier QNAP devices running QTS 4.3.4 to 4.3.6. Caused by improper limitations of a pathname to a restricted directory, this vulnerability allows for renaming arbitrary files on the target system, if exploited. QNAP have already fixed this vulnerability in the following versions: QTS 4.3.6.0895 build 20190328 (and later) QTS 4.3.4.0899 build 20190322 (and later) This issue does not affect QTS 4.4.x or QTS 4.5.x.
QNAP NAS devices running specific QTS versions are vulnerable to a file renaming flaw, allowing attackers to potentially rename arbitrary files on the system. Successful exploitation could lead to data corruption, denial of service, or unauthorized access to sensitive information. This vulnerability has been patched in newer QTS versions.
Step 1: Identify Target: The attacker identifies a vulnerable QNAP NAS device running QTS versions 4.3.4 to 4.3.6.
Step 2: Craft Malicious Request: The attacker crafts a specific HTTP request targeting the file renaming functionality. This request includes a crafted payload that specifies a new filename using path traversal techniques (e.g., ../../etc/shadow).
Step 3: Submit Request: The attacker submits the malicious HTTP request to the vulnerable QNAP NAS device.
Step 4: Vulnerable Function Execution: The QTS file renaming function receives the request and, due to the lack of proper input validation, processes the crafted filename.
Step 5: File Renaming: The file renaming function attempts to rename a file to the path specified in the malicious request. Because of the path traversal, it can rename files outside of the intended directory.
Step 6: Impact: Depending on the target file, the attacker can achieve various impacts, including data corruption, denial of service, or gaining unauthorized access to sensitive information (e.g., renaming the /etc/shadow file).
The vulnerability stems from insufficient validation of pathnames when renaming files. Specifically, the affected QTS versions fail to properly restrict the target file path to a designated directory. This allows an attacker to craft a malicious request that, when processed by the file renaming function, can specify a target file outside of the intended scope. The root cause is a path traversal vulnerability, where the software doesn't adequately sanitize or validate user-supplied input (the new filename) before using it in a system call. This leads to the ability to rename files in arbitrary locations on the filesystem. The lack of proper input validation allows an attacker to manipulate the file system.
While no specific APT groups are definitively linked to the exploitation of this specific CVE, the nature of the vulnerability makes it attractive to various threat actors. It's reasonable to assume that any group targeting NAS devices could leverage this. CISA KEV status: Not Listed.
Monitor HTTP request logs for suspicious file renaming activity, specifically looking for path traversal attempts (e.g., ../ in filenames).
Analyze system logs for unexpected file modifications or renames, especially those affecting critical system files.
Implement file integrity monitoring to detect unauthorized changes to key system files.
Network Intrusion Detection Systems (IDS) can be configured to detect malicious HTTP requests containing path traversal payloads targeting file renaming functionalities.
Examine network traffic for unusual patterns, such as a high volume of file renaming requests from a single IP address.
Update QNAP NAS devices to the latest available QTS version (4.3.6.0895 build 20190328 or later, or 4.3.4.0899 build 20190322 or later, or a QTS 4.4.x or 4.5.x version).
Implement a Web Application Firewall (WAF) to filter malicious HTTP requests containing path traversal attempts.
Regularly back up critical data to mitigate the impact of potential data corruption or loss.
Review and restrict user access privileges to minimize the impact of a successful exploit.
Enable automatic security updates to ensure the device is patched against known vulnerabilities.