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.

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

.