CVE-2025-66454
MEDIUMCVE-2025-66454 is a medium-severity (CVSS 6.5) CWE-321 vulnerability in arcade-mcp-server. O3 Security confirms whether CVE-2025-66454 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Arcade MCP Default Hardcoded Worker Secret Allows Full Unauthorized Access to All HTTP MCP Worker Endpoints
Blast Radius
arcade-mcp-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | arcade-mcp-server | all versions | 1.9.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for arcade-mcp-server. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update arcade-mcp-server to 1.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66454 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-66454 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-66454. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-66454 in your dependencies?
O3 detects CVE-2025-66454 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.