critical9.3

CVE-2025-54994

@akoskm/create-mcp-server-stdio is vulnerable to MCP Server Command Injection through `exec` API

Impact

# Command Injection in MCP Server The MCP Server at https://github.com/akoskm/create-mcp-server-stdio is written in a way that is vulnerable to command injection vulnerability attacks as part of some of its MCP Server tool definition and implementation. ## Vulnerable tool The MCP Server exposes the tool `which-app-on-port` which relies on Node.js child process API `exec` which is an unsafe and vulnerable API if concatenated with untrusted user input. Vulnerable line of code: https://github.com/akoskm/create-mcp-server-stdio/blob/main/src/index.ts#L24-L40 ```js server.tool("which-app-on-port", { port: z.number() }, async ({ port }) => { const result = await new Promise<ProcessInfo>((resolve, reject) => { exec(`lsof -t -i tcp:${port}`, (error, pidStdout) => { if (error) { reject(error); return; } const pid = pidStdout.trim(); exec(`ps -p ${pid} -o comm=`, (error, stdout) => { if (error) { reject(error); return; } resolve({ command: stdout.trim(), pid }); }); }); }); ``` ## Exploitation When LLMs are tricked through prompt injection (and other techniques and attack vectors) to call the tool with input that uses special shell characters such as `; rm -rf /tmp;#` (be careful actually executing this payload) and other payload variations, the full command-line text will be interepted by the shell and result in other commands except of `ps` executing on the host running the MCP Server. Reference example from prior security research on this topic: ![Cursor defined MCP Server vulnerable to command injection](https://res.cloudinary.com/snyk/image/upload/f_auto,w_2560,q_auto/v1747081395/Screenshot_2025-05-07_at_9.22.11_AM_d76kvm.png) ## Impact User initiated and remote command injection on a running MCP Server. ## Recommendation - Don't use `exec`. Use `execFile` instead, which pins the command and provides the arguments as array elements. - If the user input is not a command-line flag, use the `--` notation to terminate command and command-line flag, and indicate that the text after the `--` double dash notation is benign value. ## References and Prior work 1. [Exploiting MCP Servers Vulnerable to Command Injection](https://snyk.io/articles/exploiting-mcp-servers-vulnerable-to-command-injection/) 2. Liran's [Node.js Secure Coding: Defending Against Command Injection Vulnerabilities](https://www.nodejs-security.com/book/command-injection) ## Disclosed by [Liran Tal](https://lirantal.com)

Affected packages

Ecosystem	Package	Affected	Fixed in
npm	`@akoskm/create-mcp-server-stdio`	< 0.0.13	0.0.13

Weakness classification

CWE-78 CWE-77