CVE-2024-36728 in TEW-827DRU
Summary
by MITRE • 06/03/2024
TRENDnet TEW-827DRU devices through 2.06B04 contain a stack-based buffer overflow in the ssi binary. The overflow allows an authenticated user to execute arbitrary code by POSTing to apply.cgi via the action vlan_setting with a sufficiently long dns1 or dns 2 key.
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Analysis
by VulDB Data Team • 06/04/2024
The TRENDnet TEW-827DRU wireless router firmware version 2.06B04 contains a critical stack-based buffer overflow vulnerability in the ssi binary component that affects the web management interface. This vulnerability resides within the application's handling of network configuration parameters, specifically when processing POST requests to the apply.cgi endpoint with the action vlan_setting parameter. The flaw enables authenticated attackers to exploit the buffer overflow by manipulating the dns1 or dns2 configuration keys with excessively long input strings, potentially leading to arbitrary code execution on the affected device.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the ssi binary's processing logic. When the firmware receives a POST request containing the action vlan_setting parameter with malformed dns1 or dns2 values, the application fails to properly sanitize or limit the input length before copying data into fixed-size stack buffers. This classic buffer overflow condition occurs because the code does not verify that the incoming data fits within the allocated memory space, allowing an attacker to overwrite adjacent stack memory locations including return addresses and control registers. The vulnerability is classified as a stack-based buffer overflow, which aligns with CWE-121 and CWE-122 categories, representing weaknesses in memory management and input handling.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the affected network device. Once successfully exploited, the attacker can gain root-level access to the router's operating system, enabling them to modify network configurations, intercept traffic, establish persistent backdoors, or use the device as a pivot point for attacking other systems within the local network. The authenticated nature of the exploit means that an attacker must first obtain valid login credentials, but this requirement is often bypassed through credential reuse attacks, default credential exploitation, or social engineering tactics. This vulnerability directly maps to ATT&CK technique T1078.004 for valid accounts and T1059.001 for command and scripting interpreter, as the exploitation process involves executing arbitrary code and leveraging legitimate administrative access paths.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from TRENDnet, as the manufacturer has likely released patches addressing the buffer overflow conditions. Network administrators should also implement network segmentation and access control measures to limit the potential impact of successful exploitation, including restricting access to the router's management interface to trusted IP addresses only. Additional protective measures include monitoring for unusual traffic patterns or unauthorized configuration changes, implementing strong authentication mechanisms with multi-factor authentication, and conducting regular security assessments of network infrastructure to identify similar vulnerabilities in other devices. The vulnerability demonstrates the critical importance of input validation and memory safety practices in embedded systems, particularly those handling network configuration parameters that are frequently modified by administrative users. Organizations should also consider deploying network intrusion detection systems to monitor for exploitation attempts targeting known vulnerabilities in network equipment, as the specific attack vectors for this CVE involve predictable patterns of POST requests to web management interfaces.