CVE-2025-66454 json
Arcade MCP Default Hardcoded Worker Secret Allows Full Unauthorized Access to All HTTP MCP Worker Endpoints
published 2025-12-02 11 mo ago modified 2026-10-18 21 d ago also GHSA-g2jx-37x6-6438 , PYSEC-2026-1192 , EUVD-2025-200280
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 26%
- public exploits
- 0
- none known
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.
Patch / fix
- pypi arcade-mcp-server 1.9.1
- github.com/ArcadeAI/arcade-mcp@44660d1 commit
- github.com/ArcadeAI/arcade-mcp@7fb097f commit
- github.com/ArcadeAI/arcade-mcp#691 pull request
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 11 mo ago
Exploit prediction
0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
| GitHub | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
| OSV | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | arcade-mcp-server | <1.9.1 |
1.9.1 |
Affected products
- ArcadeAI arcade-mcp
Classification
References
-
github.com
/ArcadeAI/arcade-mcp/pull/691
web
-
github.com
/ArcadeAI/arcade-mcp/commit/44660d18ceb220600401303df860a31ca766c817
web
-
github.com
/ArcadeAI/arcade-mcp/commit/7fb097f20fbea35e382a1b78da6fd90609c55a9e
web
-
github.com
/ArcadeAI/arcade-mcp/security/advisories/GHSA-g2jx-37x6-6438
web
-
nvd.nist.gov
/vuln/detail/CVE-2025-66454
advisory
-
github.com
/ArcadeAI/arcade-mcp
package
-
pypi.org
/project/arcade-mcp-server
package
-
github.com
/advisories/GHSA-g2jx-37x6-6438
advisory
Sources
- CVE List CVE-2025-66454
- GitHub Advisory GHSA-g2jx-37x6-6438
- NVD CVE-2025-66454
- OSV PYSEC-2026-1192
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