Remote Command Injection in TRENDnet TEW-821DAP

A remote command injection vulnerability, identified as CVE-2026-76582, affects the TRENDnet TEW-821DAP wireless access point running firmware version 2.2.01b05. The vulnerability resides within the ssi component of the device, specifically in the /cgi-bin/ping.cgi file. The application fails to properly neutralize special shell characters in the 'ipaddr' argument before passing the user-supplied input to the popen or system functions. An authenticated remote attacker can manipulate this argument to inject and execute arbitrary system commands on the underlying operating system. The vulnerability has been publicly disclosed with a proof-of-concept exploit, increasing the risk of exploitation by threat actors targeting network infrastructure.

Attack Chain

1. Attacker performs reconnaissance to identify network-facing interfaces of vulnerable TRENDnet devices.
2. Attacker establishes a session with the device management interface using valid credentials.
3. Attacker navigates to the diagnostic ping utility located at /cgi-bin/ping.cgi.
4. Attacker crafts a malicious HTTP GET or POST request containing shell metacharacters within the 'ipaddr' parameter.
5. The ssi component fails to sanitize the 'ipaddr' input and passes the payload to a system-level function (popen or system).
6. The target device executes the injected commands with the privileges of the web service process.
7. Attacker gains persistent access or exfiltrates data from the compromised network device.

Impact

Successful exploitation allows an authenticated attacker to execute arbitrary commands with the privileges of the web server process. This can lead to full device compromise, potential lateral movement into the internal network, and unauthorized access to network traffic processed by the access point.

Recommendation

Prioritize patching or restricting access to the affected management interfaces immediately.

• Audit access logs for the /cgi-bin/ping.cgi endpoint to identify unauthorized or anomalous 'ipaddr' parameter values.
• Restrict network access to the management interfaces of all TRENDnet TEW-821DAP devices to trusted administrative IP addresses only.
• Disable the web-based management interface if not strictly required for daily operations.
• Monitor for CVE-2026-76582 exploit attempts targeting the ssi component on network perimeter devices.