A use of externally-controlled format string vulnerability has been reported to affect several QNAP operating system versions. If a remote attacker gains an administrator account, they can then exploit the vulnerability to obtain secret data or modify memory. We have already fixed the vulnerability in the following versions: QTS 5.2.7.3256 build 20250913 and later QuTS hero h5.2.7.3256 build 20250913 and later QuTS hero h5.3.1.3250 build 20250912 and later
QNAP NAS devices are vulnerable to a format string vulnerability allowing attackers with administrator privileges to potentially extract sensitive data or execute arbitrary code. This vulnerability, if exploited, could lead to complete system compromise and data exfiltration. Immediate patching is crucial to mitigate the risk.
Step 1: Account Compromise: The attacker must first gain access to an administrator account on the QNAP device. This could be achieved through various means, such as brute-forcing weak passwords, exploiting other vulnerabilities, or social engineering.
Step 2: Payload Delivery: Once administrator access is obtained, the attacker crafts a malicious input string containing format string specifiers. This input is then submitted to a vulnerable function or service on the QNAP device. The exact method of delivery depends on the specific vulnerable component.
Step 3: Format String Exploitation: The vulnerable function processes the attacker-controlled input as a format string. The format string specifiers allow the attacker to read from the device's memory (e.g., using %x to leak data) or write to arbitrary memory locations (e.g., using %n to overwrite data). This can be used to obtain sensitive information, such as passwords or encryption keys, or to overwrite critical program data, potentially leading to code execution.
Step 4: Code Execution (Optional): If the attacker successfully overwrites critical program data, they can potentially redirect program execution to a malicious code payload, gaining full control of the device.
The vulnerability stems from a failure to properly sanitize user-supplied input before passing it to a function that interprets format string specifiers (e.g., printf, fprintf). Specifically, the affected code likely uses a user-controlled string as the format argument. An attacker can craft a malicious input containing format string specifiers (e.g., %x, %s, %n) to read from or write to arbitrary memory locations. The root cause is the lack of input validation and sanitization, allowing an attacker to control the format string and manipulate the program's memory. This is a classic example of a format string vulnerability, leading to potential information disclosure and code execution.