Buffer Overflow in TRENDnet TEW-821DAP

Executive Summary

CVE-2026-15484 is a buffer overflow vulnerability found in the Trendnet TEW-821DAP device running firmware version 1.12B01. The issue occurs in the function sub_41EC14 within the ssi program, specifically in the /goform/tools_nslookup component. A buffer of only 2 bytes is used to store a command string that is actually 33 bytes long, causing a buffer overflow. This overflow is triggered remotely via an HTTP POST request to /goform/tools_nslookup, which calls the vulnerable function. The overflow happens when the setenv function sets the host variable and sprintf constructs the command string.

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Impact Analysis

This vulnerability can allow an attacker to remotely execute arbitrary code or cause a denial of service on the affected device by exploiting the buffer overflow. Because the overflow occurs during the construction of a command string, it may lead to system compromise or instability. However, this vulnerability only affects devices that are no longer supported by the vendor.

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Detection Guidance

This vulnerability can be detected by monitoring for HTTP POST requests to the endpoint /goform/tools_nslookup on the Trendnet TEW-821DAP device running firmware version v1.12B01.

Specifically, detection involves identifying attempts to exploit the buffer overflow in the function sub_41EC14 triggered by crafted POST requests that manipulate the host parameter used in the nslookup command.

A suggested command to detect such activity on the device or network could be to capture and analyze HTTP POST requests targeting /goform/tools_nslookup, for example using network monitoring tools like tcpdump or Wireshark with filters for POST requests to that path.

• tcpdump -i <interface> -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep 'POST /goform/tools_nslookup'

Additionally, inspecting device logs for unusual or malformed nslookup command executions or buffer overflow symptoms may help detect exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include restricting or blocking HTTP POST requests to the /goform/tools_nslookup endpoint on the affected Trendnet TEW-821DAP devices.

Since the vulnerability is triggered remotely via this endpoint, network-level controls such as firewall rules or access control lists can prevent exploitation attempts.

Additionally, because the affected products are no longer supported by the vendor, applying official patches or firmware updates may not be possible.

Therefore, isolating the vulnerable device from untrusted networks or replacing it with a supported device are recommended longer-term mitigation strategies.

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