OAuth Vulnerability in Cloudflare MCP Framework Workers
CVE-2025-4144

5.3MEDIUM

Key Information:

Vendor

Cloudflare

Status
Vendor
CVE Published:
1 May 2025

What is CVE-2025-4144?

The PKCE (Proof Key for Code Exchange) mechanism, designed to enhance the security of OAuth implementations, has been compromised in the workers-oauth-provider of the MCP framework. An attacker can leverage this vulnerability to bypass the essential PKCE checks, thereby undermining the defenses against certain types of OAuth-related attacks. This flaw highlights the importance of stringent security measures within OAuth 2.1 requirements, as the bypass of PKCE can lead to unauthorized access and potential data breaches.

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References

https://github.com/cloudflare/workers-oauth-provider/pull/27

CVSS V4

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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