Executive Summary

[{'type': 'paragraph', 'content': "CVE-2026-4192 is a command injection vulnerability found in version 1.0.0 of the AvinashBole quip-mcp-server. It affects the function setupToolHandlers in the file src/index.ts. The vulnerability arises because the application uses Node.js's child_process.exec function unsafely by directly incorporating user-controlled inputs into shell commands without proper validation or sanitization."}, {'type': 'paragraph', 'content': 'Specifically, parameters like threadId and content in various MCP server tools (quip_read_document, quip_append_content, quip_prepend_content, and quip_replace_content) are concatenated into shell commands executed asynchronously. This allows attackers to inject shell metacharacters such as &, ;, and &&, enabling arbitrary command execution on the server remotely.'}, {'type': 'paragraph', 'content': 'The vulnerability is publicly disclosed with proof-of-concept exploits demonstrating how malicious input can execute arbitrary commands, such as creating files or running system commands with the privileges of the MCP server process.'}] [1, 2, 3, 5]

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Impact Analysis

This vulnerability allows remote attackers to execute arbitrary commands on the server running the quip-mcp-server application. Such unauthorized command execution can lead to several impacts:

• Compromise of server confidentiality by accessing sensitive data.
• Integrity violations by modifying data or system files.
• Availability issues by disrupting or damaging the server environment.
• Potential full control over the host system depending on the privileges of the MCP server process.

Because the vulnerability can be exploited remotely without user interaction, it poses a significant risk to systems running the affected software.

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Compliance Impact

I don't know

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Detection Guidance

This vulnerability can be detected by testing for command injection in the parameters `threadId` and `content` used by the quip-mcp-server tools such as quip_read_document, quip_append_content, quip_prepend_content, and quip_replace_content.

A practical detection method is to inject shell metacharacters into these parameters and observe if arbitrary commands are executed. For example, injecting a payload like `valid_id&whoami > poc.txt&REM` into the `threadId` parameter can cause the server to execute the `whoami` command and write its output to a file named `poc.txt`.

To detect exploitation on your system, you can check for unexpected files such as `poc.txt` or other artifacts created by injected commands.

Suggested commands to test or detect the vulnerability include sending crafted requests to the MCP server with injected shell commands in the vulnerable parameters and monitoring the server filesystem or process execution logs for signs of command execution.

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Mitigation Strategies

[{'type': 'paragraph', 'content': "Immediate mitigation steps include avoiding the use of Node.js's child_process.exec function with user-controlled inputs."}, {'type': 'list_item', 'content': 'Replace exec with execFile, which allows specifying commands and arguments as separate array elements, reducing the risk of shell command injection.'}, {'type': 'list_item', 'content': 'Implement strict input validation and sanitization on all parameters exposed to MCP clients, especially the `threadId` and `content` parameters.'}, {'type': 'list_item', 'content': 'Use parameter separation and proper escaping techniques to prevent shell metacharacters from being interpreted by the shell.'}, {'type': 'paragraph', 'content': 'Since no patched versions are currently available, consider restricting network access to the quip-mcp-server or replacing it with a secure alternative until a fix is released.'}] [1, 2]

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