How severe is CVE-2025-66454?

CVE-2025-66454 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2025-66454 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2025-66454?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-66454 have an EU (EUVD) identifier?

Yes. CVE-2025-66454 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-200280.

When was CVE-2025-66454 published?

CVE-2025-66454 was published on 2025-12-02 and last updated on 2026-06-17.

CVE-2025-66454

CVE-2025-66454 is a medium-severity vulnerability with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-321.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-200280
Weakness: CWE-321
Published: 2025-12-02
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-66454?: CVE-2025-66454 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2025-66454 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-66454?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66454 have an EU (EUVD) identifier?: Yes. CVE-2025-66454 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-200280.
When was CVE-2025-66454 published?: CVE-2025-66454 was published on 2025-12-02 and last updated on 2026-06-17.

References

Other CWE-321 vulnerabilities

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