Most recent entries from all

EUVD-2026-262330

fkie_cve-2025-66454

Arcade MCP allows you to to create, deploy, and share MCP Servers. Prior to 1.5.4, the arcade-mcp HTTP server uses a hardcoded default worker secret ("dev") that is never validated or overridden during normal server startup. As a result, any unauthenticated attacker who knows this default key can forge valid JWTs and fully bypass the FastAPI authentication layer. This grants remote access to all worker endpoints—including tool enumeration and tool invocation—without credentials. This vulnerability is fixed in 1.5.4.

GHSA-g2jx-37x6-6438 — arcade-mcp-server Has Default Hardcoded Worker Secret That Allows Full Unauthorized Access to All HTTP MCP Worker Endpo…

Affected: PyPI: arcade-mcp-server

### Summary

The arcade-mcp HTTP server uses a hardcoded default worker secret ("dev") that is never validated or overridden during normal server startup. As a result, any unauthenticated attacker who knows this default key can forge valid JWTs and fully bypass the FastAPI authentication layer. This grants remote access to all worker endpoints—including tool enumeration and tool invocation—without credentials.

Anyone following the official quick-start guide is vulnerable unless they manually override ARCADE_WORKER_SECRET.

### Details

The documented method for launching an HTTP MCP server (python server.py http) implicitly sets the worker secret to the hardcoded default "dev":

ArcadeSettings.server_secret defaults to "dev" (libs/arcade-mcp-server/arcade_mcp_server/settings.py:129–158)

create_arcade_mcp() passes this value directly to FastAPIWorker without validation (libs/arcade-mcp-server/arcade_mcp_server/worker.py:118–188)

BaseWorker._set_secret() accepts this value and does not enforce rotation (libs/arcade-serve/arcade_serve/core/base.py:42–83)

Because the worker’s signing key is constant and publicly documented, attackers can trivially generate valid HS256 JWTs:

The FastAPI worker auth middleware (arcade_serve/fastapi/auth.py) trusts any JWT signed with the worker secret.

The core auth layer (arcade_serve/core/auth.py) does not distinguish forged tokens from legitimate ones.

The official quick-start instructions (README.md:164–190) demonstrate launching an MCP…

PYSEC-2026-1192 — arcade-mcp-server Has Default Hardcoded Worker Secret That Allows Full Unauthorized Access to All HTTP MCP Worker Endpo…