What is CVE-2025-66454?

CVE-2025-66454 is a medium-severity vulnerability in Arcadeai Arcade-Mcp, classified under Use of Hard-coded Cryptographic Key. CVSS score: 6.5/10. Published 2025-12-02.

How severe is CVE-2025-66454?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Arcadeai Arcade-Mcp

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.

Published 2025-12-02 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (21.9th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 22nd percentile — 21.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Arcadeai Arcade-Mcp — versions < 1.5.4

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2025-66454?: CVE-2025-66454 is a medium-severity vulnerability in Arcadeai Arcade-Mcp, classified under Use of Hard-coded Cryptographic Key. CVSS score: 6.5/10. Published 2025-12-02.
How severe is CVE-2025-66454?: Medium severity. CVSS v3 base score is 6.5 out of 10.