---
title: "GHSA-wvr4-3wq4-gpc5: MCP Connect has unauthenticated remote OS command execution via /bridge endpoint"
url: https://erroneo.us/security/ghsa/GHSA-wvr4-3wq4-gpc5/
description: "GHSA-wvr4-3wq4-gpc5 (critical, npm): MCP Connect has unauthenticated remote OS command execution via /bridge endpoint. Summary When AUTHTOKEN and…"
type: advisory
section: "Security Digest"
date_published: 2026-03-19
date_modified: 2026-03-19
publisher: erroneo.us
author: erroneo.us Security Desk
ghsa: "GHSA-wvr4-3wq4-gpc5"
license: All rights reserved. Quote with attribution and a link.
---

# GHSA-wvr4-3wq4-gpc5: MCP Connect has unauthenticated remote OS command execution via /bridge endpoint

## Affected packages

- npm `mcp-bridge` <= 2.0.0 → fixed: none listed

## Details

Summary When AUTHTOKEN and ACCESSTOKEN environment variables are not set (which is the default out-of-the-box configuration) the /bridge HTTP endpoint is completely unauthenticated. Any network-accessible caller can POST a request with an attacker-controlled serverPath and args payload, causing the server to spawn an arbitrary OS process as the user running mcp-bridge. This results in full remote code execution on the host without any credentials. Details Root cause 1 - Authentication not enforced when token is absent src/config/config.ts line 161 sets authToken to an empty string when neither environment variable is configured: The auth middleware in src/server/http-server.ts lines 118–141 wraps all enforcement in if (this.accessToken). Because an empty string is falsy in JavaScript, the entire block is skipped and next() is called unconditionally for every request: The only consequence of a missing token is a log warning (line 42–43). The server starts and serves requests normally. Root cause 2 - /bridge spawns arbitrary processes from request body input src/server/http-server.ts lines 194 and 218/227 extract serverPath and args directly from the untrusted JSON body and pass them to MCPClientManager.createClient() without any validation: src/client/mcp-client-manager.ts lines 68–75 fall through to StdioClientTransport for any value that is not a valid HTTP/WS URL, using serverPath as the executable command verbatim: There is no allow-list, no path restriction, and no sanitization. Any binary reachable from the server's PATH (including bash, sh, python, node, etc) can be invoked with arbitrary arguments. Exposure surface Express's app.listen(port) binds to all interfaces (0.0.0.0) by default, making the service immediately reachable over the network on any cloud VM or container. The project additionally ships an explicit start:tunnel npm script that uses ngrok to publish the server to a public internet URL, maximising the attack surface. PoC Start the server with no auth token configured (the default): Send a crafted request from any machine that can reach port 3000: The server spawns bash as the mcp-bridge process user. The command executes, the file is written, and the HTTP response will contain the error from the MCP handshake failing (but the payload has already run). For…

## Sources

- [GitHub Advisory GHSA-wvr4-3wq4-gpc5](https://github.com/advisories/GHSA-wvr4-3wq4-gpc5)
- [github.com](https://github.com/EvalsOne/MCP-connect/security/advisories/GHSA-wvr4-3wq4-gpc5)

---
Source page: https://erroneo.us/security/ghsa/GHSA-wvr4-3wq4-gpc5/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt