Can you explain this vulnerability to me?

[{'type': 'paragraph', 'content': 'CVE-2026-4199 is a command injection vulnerability found in the bazinga012 mcp_code_executor project, specifically in the installDependencies function of the src/index.ts file. The vulnerability arises because the software constructs shell commands by directly concatenating user-controlled input (package names) into command strings executed via a shell. This unsafe practice allows an attacker with local access to inject arbitrary shell commands by crafting malicious package names containing shell metacharacters.'}, {'type': 'paragraph', 'content': "The vulnerability is triggered when the install_dependencies tool uses Node.js's child_process.execAsync to run commands like conda install or pip install with user input. Since execAsync runs commands through a shell, injected commands can be executed with the same privileges as the MCP server process. The issue is due to improper sanitization and direct interpolation of untrusted input into shell commands."}, {'type': 'paragraph', 'content': "A proof of concept demonstrates that input such as 'numpy&whoami > poc.txt' in the packages parameter causes execution of the injected whoami command, writing its output to a file. The vulnerability can lead to arbitrary command execution, unauthorized data access, or modification of the host environment."}, {'type': 'paragraph', 'content': 'The vulnerability only allows local exploitation and affects versions up to 0.3.0. A patch replaces execAsync with execFileAsync, which executes commands without a shell by passing arguments as arrays, preventing shell interpretation and command injection.'}] [1, 2, 3, 4, 5]

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How can this vulnerability impact me? :

Successful exploitation of this vulnerability allows an attacker with local access to execute arbitrary shell commands on the MCP server host with the same privileges as the MCP server process.

• Execution of arbitrary commands leading to unauthorized data access.
• Modification or disruption of the server environment.
• Potential full system compromise depending on the privileges of the MCP server process.

Because the exploit is easy to perform and a proof of concept is publicly available, the risk is significant if the vulnerability is not patched. However, exploitation requires local access, limiting remote attack vectors.

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How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:

I don't know

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability involves command injection through the installDependencies function in the mcp_code_executor tool, specifically via the packages parameter. Detection can focus on monitoring for suspicious command executions or unexpected file creations triggered by injected shell commands.

A proof of concept demonstrated injecting commands like `numpy&whoami > poc.txt` into the packages field, which causes execution of the `whoami` command and writes output to a file named poc.txt. Monitoring for such unexpected files or command executions can help detect exploitation attempts.

Suggested detection commands include searching for suspicious files created by injected commands, for example:

• Check for unexpected files like poc.txt in the code storage directory: `find /path/to/code_storage -name poc.txt`
• Monitor running processes for suspicious commands or shell executions related to package installation.
• Audit logs or command histories for unusual package installation commands containing shell metacharacters such as `;`, `&`, or `|`.

Since the vulnerability requires local access and is triggered by local environment commands, network detection may be limited. Instead, focus on system-level monitoring and auditing of the mcp_code_executor usage and its install_dependencies tool.

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What immediate steps should I take to mitigate this vulnerability?

The primary mitigation is to apply the available patch that replaces the unsafe use of child_process.execAsync with child_process.execFileAsync in the installDependencies function. This change avoids shell interpretation of user inputs by passing command arguments as arrays rather than concatenated shell strings.

Additional immediate steps include:

• Avoid using execAsync or any shell command execution that interpolates user input directly.
• Implement strict input validation and sanitization on all parameters, especially the packages parameter, to prevent injection of shell metacharacters.
• Use parameter separation and proper escaping techniques to ensure user inputs cannot be interpreted as shell commands.
• Restrict local access to the environment where mcp_code_executor runs to trusted users only, as exploitation requires local environment access.

Applying the patch from the official GitHub repository is strongly recommended to eliminate the vulnerability while preserving functionality.

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