BurtTheCoder mcp-dnstwist OS Command Injection via Request Argument

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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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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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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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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