Arcade MCP Default Hardcoded Worker Secret Allows Full Unauthorized Access to All HTTP MCP Worker Endpoints
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-321.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| ArcadeAI | arcade-mcp | before 1.5.4 | 1.5.4 | Patch available | CNA |
| — | arcade-mcp-server (PyPI) | before 1.9.1 | 1.9.1 | Patch available | GHSA-g2jx-37x6-6438 |
- arcade-mcp VendorArcadeAI Affected before 1.5.4 Fixed in 1.5.4 Patch available CNA
- arcade-mcp-server (PyPI) Vendor— Affected before 1.9.1 Fixed in 1.9.1 Patch available GHSA-g2jx-37x6-6438
Remediation
- Fix · CNA arcade-mcp (ArcadeAI) Fixed in 1.5.4
- Fix · GHSA-g2jx-37x6-6438 arcade-mcp-server (PyPI) Fixed in 1.9.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2025-66454
- 2026-10-03 Alias added: GHSA-g2jx-37x6-6438
References
Other 5
- 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
- https://github.com/ArcadeAI/arcade-mcp/commit/7fb097f20fbea35e382a1b78da6fd90609c55a9e
- https://github.com/ArcadeAI/arcade-mcp
Sources
- CVE-2025-66454 · CVE Program
- CVE-2025-66454 · NVD
- FIRST EPSS
- GHSA-g2jx-37x6-6438 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences