Executive Summary

The CVE-2026-7124 vulnerability affects the TOTOLINK A8000RU router, version 7.1cu.643_b20200521. It is a command injection flaw located in the cstecgi.cgi CGI script, specifically in the function that processes the addrPrefixLen parameter.

An attacker can send a specially crafted HTTP POST request to the /cgi-bin/cstecgi.cgi endpoint with malicious shell commands embedded in the addrPrefixLen parameter. This causes the router to execute arbitrary operating system commands.

For example, an attacker can execute commands like listing directory contents and saving the output to a file on the device, demonstrating the ability to run arbitrary commands remotely.

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Impact Analysis

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

• Attackers can gain unauthorized control over the device.
• They can manipulate router configurations or disrupt network operations.
• Sensitive information stored or passing through the router could be exposed or altered.
• It poses a significant security risk to the network and connected devices.

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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 with the parameter addrPrefixLen containing a command injection payload.

For example, you can test the vulnerability by sending a POST request with addrPrefixLen set to a command like `ls>./setIpv6LanCfg.txt`. If the router is vulnerable, it will execute the command and create a file named setIpv6LanCfg.txt containing the directory listing.

• Use curl or a similar tool to send the test POST request: curl -X POST http://<router-ip>/cgi-bin/cstecgi.cgi -d "addrPrefixLen=ls>./setIpv6LanCfg.txt"
• Check the router's file system for the presence of the file setIpv6LanCfg.txt to confirm command execution.

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Compliance Impact

The CVE-2026-7124 vulnerability allows remote attackers to execute arbitrary operating system commands on the affected TOTOLINK A8000RU router. This type of vulnerability can lead to unauthorized access, data manipulation, or data exfiltration, which may compromise the confidentiality, integrity, and availability of sensitive information.

Such security breaches can negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require organizations to protect personal and sensitive data against unauthorized access and ensure the security of their IT systems.

Therefore, if exploited, this vulnerability could result in violations of these regulations due to potential data breaches or loss of control over protected information.

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Mitigation Strategies

To mitigate the CVE-2026-7124 vulnerability in the TOTOLINK A8000RU router, immediate steps include restricting remote access to the affected CGI interface to prevent exploitation.

Avoid exposing the /cgi-bin/cstecgi.cgi endpoint to untrusted networks or the internet.

Implement network-level controls such as firewall rules to block unauthorized HTTP POST requests targeting the vulnerable function.

Monitor the device for suspicious files or activities, such as unexpected files like setIpv6LanCfg.txt, which may indicate exploitation attempts.

Check for and apply any available firmware updates or patches from the vendor that address this vulnerability.

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