The security vulnerability at the heart of this post, CVE-2022-4221, affects Asus NAS-M25 Network-attached Storage (NAS) devices. This is because of a critical flaw: "Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')" allows unauthenticated attackers to exploit arbitrary OS commands via unsanitized cookie values.

The affected version of Asus NAS-M25 is up through 1..1.7. In this post, we will dissect this vulnerability, providing code snippets for illustration, links to original references, and a detailed analysis of the resulting exploit.

Vulnerability Details

The weakness in question, "Improper Neutralization of Special Elements used in an OS Command," also known as "OS Command Injection," is essentially allowing an attacker to inject malicious code into the operating system's command line interface. This can occur when an application passes these special elements (such as unsanitized user input) to the OS command interpreter. In our case, the Asus NAS-M25 is the vulnerable device, and the unsanitized cookies passed to the OS command interpreter are the entry point for attackers.

Exploit Details

Unauthenticated attackers can exploit this vulnerability by sending malicious cookies with arbitrary Operating System (OS) commands as part of an HTTP request. Since the NAS-M25 device does not sanitize the received cookie values, the attacker's payload is executed by the OS command interpreter. The following is a simplified example of how attackers can exploit this vulnerability:


GET / HTTP/1.1

Send the malicious request to the victim's NAS-M25 device.

3. If successful, the OS command interpreter will execute the attacker's payload alongside the system commands.

The impact of a successful attack varies, depending on the injected commands. Attackers may escalate privileges, extract sensitive data, or execute remote code on the target NAS-M25 device.

Ensure the most recent firmware version (1..1.7) is installed on your NAS-M25 device.

- Disallow access to the NAS-M25 admin panel from untrusted networks, or limit access to a restricted set of IP addresses.

For the long-term solution, users are encouraged to follow Asus for the release of a firmware patch that addresses this issue.

The original vulnerability report can be found here

- CVE-2022-4221 - National Vulnerability Database (NVD)
- ASUSTOR NAS devices OS Command Injection
- ASUS NAS-M25 Manual - Firmware Upgrade Section


The CVE-2022-4221 vulnerability of Asus NAS-M25 devices is a serious security flaw that requires its users to apply the necessary precautions and stay informed about software updates and potential fixes. It highlights the importance of proper input validation and sanitization in web applications, even those intended for administration purposes. By following the mitigation steps provided and keeping up to date with firmware patches, NAS-M25 users can effectively minimize the risk of this vulnerability being exploited.


Published on: 12/01/2022 10:15:00 UTC
Last modified on: 12/05/2022 15:11:00 UTC