Source: security@qnapsecurity.com.tw
An allocation of resources without limits or throttling vulnerability has been reported to affect several QNAP operating system versions. If a remote attacker gains a user account, they can then exploit the vulnerability to prevent other systems, applications, or processes from accessing the same type of resource. We have already fixed the vulnerability in the following versions: QTS 5.2.6.3195 build 20250715 and later QuTS hero h5.2.6.3195 build 20250715 and later
QNAP NAS devices are vulnerable to a denial-of-service (DoS) attack due to an unrestricted resource allocation flaw. An authenticated attacker can exhaust system resources, preventing legitimate users and services from functioning, leading to data unavailability and potential business disruption.
Step 1: Account Compromise: The attacker gains access to a valid user account on the QNAP device. This could be achieved through various means, such as credential stuffing, brute-force attacks, or exploiting other vulnerabilities.
Step 2: Identify Vulnerable Resource: The attacker identifies the specific resource that is susceptible to uncontrolled allocation. This might involve reverse engineering the QNAP firmware or analyzing network traffic to understand how the system allocates resources.
Step 3: Craft Malicious Requests: The attacker crafts a series of requests designed to consume the targeted resource at an excessive rate. These requests are designed to trigger the vulnerable function repeatedly.
Step 4: Resource Exhaustion: The crafted requests are sent to the QNAP device. The vulnerable function processes these requests without proper limits, leading to the rapid depletion of the targeted resource.
Step 5: Denial of Service: As the resource is exhausted, the QNAP device becomes unresponsive or experiences performance degradation. Legitimate users and services are unable to access the resource, resulting in a DoS condition.
The vulnerability stems from a lack of resource limits or throttling mechanisms within the QNAP operating system. Specifically, the affected code fails to properly validate or restrict the amount of a particular resource (e.g., memory, file handles, network connections) that a user account can consume. This allows an authenticated attacker to craft requests that consume excessive resources, leading to resource exhaustion. The root cause is likely a missing or inadequate check within a critical system function responsible for allocating or managing the targeted resource. This could be related to a specific service, process, or API call that handles resource allocation. The absence of rate limiting or quota enforcement allows the attacker to repeatedly trigger the vulnerable function, rapidly depleting the available resources and causing a DoS condition. The specific resource affected is not explicitly stated, but the description implies it's a shared resource critical for system operation.
While no specific APT groups are directly linked to this vulnerability at this time, any threat actor with access to QNAP devices could potentially exploit it. This includes financially motivated cybercriminals, state-sponsored actors, and opportunistic attackers. The lack of a public PoC suggests that exploitation is currently limited to those with internal knowledge or the ability to reverse engineer the affected systems. CISA KEV status: Not Applicable (as of this analysis).
Monitor system logs for unusual activity from user accounts, particularly those with administrative privileges.
Analyze network traffic for patterns of excessive requests to specific services or ports.
Monitor resource utilization (CPU, memory, disk I/O, network bandwidth) for sudden spikes or sustained high usage.
Implement intrusion detection systems (IDS) with rules to identify suspicious activity related to resource allocation.
Review system logs for error messages related to resource exhaustion (e.g., 'out of memory', 'too many open files').
Monitor for failed login attempts and suspicious account activity.
Upgrade to the patched QTS or QuTS hero versions: QTS 5.2.6.3195 build 20250715 and later; QuTS hero h5.2.6.3195 build 20250715 and later.
Implement strong password policies and enforce multi-factor authentication (MFA) for all user accounts.
Regularly review user accounts and permissions, removing unnecessary accounts and limiting privileges.
Monitor system logs and network traffic for suspicious activity.
Implement rate limiting or throttling mechanisms on critical services to prevent resource exhaustion.
Consider deploying a web application firewall (WAF) to filter malicious requests.
Isolate the QNAP device on a separate network segment to limit the impact of a potential attack.
Regularly back up data to ensure business continuity in case of a DoS attack.