Detection Guidance

This vulnerability can be detected by monitoring for unusual or suspicious command execution patterns originating from the MCP interface, especially commands that include shell metacharacters injected via user-controlled parameters such as nameservers.

A practical approach is to analyze logs or network traffic for attempts to invoke the fuzz_domain function with crafted input containing shell metacharacters.

Since the vulnerability involves command injection through the child_process.exec call with arguments joined as a string, detection commands could include searching for processes or logs that show unexpected shell commands executed by the MCP server process.

Example commands to detect exploitation attempts might include:

• Using system process monitoring to detect suspicious child processes spawned by the MCP server, e.g., `ps aux | grep mcp-dnstwist` and checking for unusual commands.
• Searching logs for suspicious input patterns, e.g., `grep -E 'nameservers=.*[;&|$`]' /var/log/mcp-dnstwist.log` to find injected shell metacharacters.
• Network monitoring for unusual DNS fuzzing requests containing suspicious payloads.

Because the vulnerability requires network access to the MCP interface and crafted input, monitoring incoming requests to the MCP server for suspicious parameters is critical.

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Executive Summary

This vulnerability exists in the BurtTheCoder mcp-dnstwist software up to version 1.0.4, specifically in the fuzz_domain function within the src/index.ts file of the MCP Interface component.

It allows an attacker to manipulate the argument Request in a way that leads to operating system command injection.

This means that an attacker can remotely execute arbitrary OS commands on the affected system by exploiting this weakness.

The exploit code for this vulnerability has been made publicly available, increasing the risk of attacks.

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Impact Analysis

This vulnerability can have serious impacts because it allows remote attackers to execute arbitrary operating system commands on the affected system.

Such command injection can lead to unauthorized access, data theft, data modification, system compromise, or disruption of services.

Since the exploit is publicly available, the risk of exploitation is higher, potentially leading to significant security breaches.

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Compliance Impact

The vulnerability allows remote OS command injection, potentially leading to full host compromise including data exposure, integrity loss, and service disruption.

Such impacts on confidentiality, integrity, and availability of data can negatively affect compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive data and system integrity.

Failure to mitigate this vulnerability could result in unauthorized access to personal or protected health information, violating regulatory requirements.

Mitigations such as restricting access, strict input validation, and avoiding unsafe command execution are necessary to maintain compliance.

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Executive Summary

CVE-2026-7443 is an OS Command Injection vulnerability in the mcp-dnstwist tool by BurtTheCoder, which is used for DNS fuzzing to detect typosquatting and phishing. The vulnerability occurs because the tool improperly handles user-controlled input parameters, such as nameservers, by concatenating them into a shell command string and executing it without proper escaping or validation. This allows an attacker to inject malicious shell commands that the server process will execute.

The flaw is located in the fuzz_domain function of the MCP Interface component, specifically in the src/index.ts file. An attacker with network access to the MCP interface can exploit this by sending crafted input containing shell metacharacters, leading to arbitrary command execution on the host system.

No fixed version is currently available, and the vulnerability has been publicly disclosed with proof of concept exploits. Mitigations include restricting access, validating inputs strictly, and avoiding shell-interpreted command execution.

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Impact Analysis

This vulnerability can have severe impacts including full host compromise. An attacker exploiting this flaw can execute arbitrary OS commands with the privileges of the MCP server process.

• Unauthorized code execution on the host system.
• Exposure of sensitive data.
• Loss of data integrity.
• Disruption of service availability.

The attack can be launched remotely by anyone with network access to the MCP interface, making it a critical risk if the server is exposed to untrusted clients.

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Detection Guidance

This vulnerability can be detected by testing the MCP interface's fuzz_domain function for command injection via the nameservers parameter. Since the vulnerability involves injection through shell commands constructed with user input, detection involves attempting to inject shell metacharacters or commands and observing if they are executed.

A proof of concept involves injecting crafted shell commands into the nameservers parameter and checking for execution results, such as retrieving the server process's UID/GID or other command outputs.

Suggested detection commands include sending requests to the MCP interface with payloads that include shell metacharacters or base64-encoded commands to verify if arbitrary command execution is possible.

• Inject shell commands via the nameservers parameter, for example: nameservers="; id; #" or nameservers="$(id)"
• Check for command execution by observing output or side effects, such as retrieving user or process information.
• Use base64-encoded commands to confirm execution, e.g., injecting commands that output base64-encoded UID/GID.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the MCP server to trusted clients only and not exposing it to untrusted networks.

Apply strict input validation and allowlisting on all user-controlled parameters, especially the nameservers parameter, to prevent injection of shell metacharacters.

Avoid using shell-interpreted command lines by replacing child_process.exec with safer alternatives such as child_process.spawn or child_process.execFile with shell set to false.

Implement sandboxing and other security measures to limit the impact of potential exploitation.

Monitor for updates or patches from the project, although no fixed version is currently available.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the MCP server to trusted clients only, ensuring it is not exposed to untrusted networks.

Implement strict input validation and allowlisting on all user-controlled parameters, especially those passed to the fuzz_domain function, to prevent injection of shell metacharacters.

Avoid using shell-interpreted command lines by replacing child_process.exec with safer alternatives such as child_process.spawn or child_process.execFile with shell set to false.

If possible, update to a fixed version once it becomes available; currently, no fixed version exists.

Additional security measures include sandboxing the MCP server process and monitoring for suspicious activity.

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