GHSA-6jx8-rcjx-vmwf

The MCP Server at https://github.com/Sunwood-ai-labs/github-kanban-mcp-server/ 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 `add_comment` which relies on Node.js child process API `exec` to execute the GitHub (`gh`) command, is an unsafe and vulnerable API if concatenated with untrusted user input. Data flows from the tool definition [here](https://github.com/Sunwood-ai-labs/github-kanban-mcp-server/blob/main/src/handlers/tool-handlers.ts#L79) which takes in `args.issue_number` and calls `handleAddComment()` in [this definitino](https://github.com/Sunwood-ai-labs/github-kanban-mcp-server/blob/main/src/handlers/comment-handlers.ts#L8) that uses `exec` in an insecure way. Vulnerable line of code: https://github.com/Sunwood-ai-labs/github-kanban-mcp-server/blob/main/src/handlers/comment-handlers.ts#L8-L23 ```js export async function handleAddComment(args: { repo: string; issue_number: string; body: string; state?: 'open' | 'closed'; }): Promise<ToolResponse> { const tempFile = 'comment_body.md'; try { // ステータスの変更が指定されている場合は先に処理 if (args.state) { try { const command = args.state === 'closed' ? 'close' : 'reopen'; await execAsync( `gh issue ${command} ${args.issue_number} --repo ${args.repo}` ); ``` ## Exploitation Proof of Concept 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, demonstrating how a similarly vulnerable MCP Server connected to Cursor is abused with prompt injection to bypass the developer's intended command:  ## 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) ## Credit Disclosed by [Liran Tal](https://lirantal.com)