Executive Summary

CVE-2026-35906 is a critical vulnerability in T3 Technology CPE devices such as the T625Pro, T6825G, T628, and T628L. It involves an undocumented debug CGI endpoint located at /cgi-bin/shortcut_telnet.cgi that allows unauthenticated attackers to execute arbitrary system commands as the root user by supplying a specially crafted HTTP query string.

This flaw exists because the endpoint lacks authentication and exposes debug code that executes user-supplied commands with root privileges. The vulnerability can be exploited remotely, even through Blind CSRF attacks, where an attacker tricks a user into triggering the exploit by visiting a malicious webpage.

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Impact Analysis

Exploitation of this vulnerability can lead to full compromise of the affected device. An attacker can execute arbitrary commands as root, which may result in credential theft, establishing persistence on the device, and lateral movement within the victim's network.

This can severely impact the confidentiality, integrity, and availability of the device and the network it is connected to, potentially allowing attackers to control network traffic, steal sensitive information, or disrupt services.

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Detection Guidance

This vulnerability can be detected by checking for the presence of the undocumented debug CGI endpoint `/cgi-bin/shortcut_telnet.cgi` on affected T3 Technology CPE devices.

You can attempt to detect the vulnerability by sending crafted HTTP requests to this endpoint and observing if arbitrary commands are executed without authentication.

For example, you might use curl or similar tools to test the endpoint:

• curl -v "http://<device-ip>/cgi-bin/shortcut_telnet.cgi?cmd=id"
• curl -v "http://<device-ip>/cgi-bin/shortcut_telnet.cgi?cmd=uname -a"

If the response contains output from these commands, it indicates the device is vulnerable.

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Mitigation Strategies

Immediate mitigation steps include removing or disabling the undocumented debug CGI endpoint `/cgi-bin/shortcut_telnet.cgi` to prevent unauthenticated command execution.

Enforce authentication on all CGI endpoints to ensure only authorized users can access sensitive functions.

Restrict access to the CPE management interface by limiting it to trusted networks or using firewall rules.

Since no patch is available as of the disclosure date, consider isolating affected devices from untrusted networks and monitoring for suspicious activity.

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Compliance Impact

This vulnerability allows unauthenticated remote code execution as root on affected T3 Technology CPE devices, leading to full device compromise.

Such a compromise can result in credential theft, persistence, and lateral movement within the network, severely impacting confidentiality, integrity, and availability of data.

Given these impacts, organizations using these devices may face challenges in maintaining compliance with standards and regulations like GDPR and HIPAA, which require protection of sensitive data and secure system integrity.

Failure to remediate this vulnerability could lead to unauthorized access and data breaches, potentially resulting in violations of these regulations.

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