CVE-2025-4144

Description

PKCE was implemented in the OAuth implementation in workers-oauth-provider that is part of MCP framework https://github.com/cloudflare/workers-mcp . However, it was found that an attacker could cause the check to be skipped. Fixed in: https://github.com/cloudflare/workers-oauth-provider/pull/27 https://github.com/cloudflare/workers-oauth-provider/pull/27 Impact: PKCE is a defense-in-depth mechanism against certain kinds of attacks and was an optional extension in OAuth 2.0 which became required in the OAuth 2.1 draft. (Note that the MCP specification requires OAuth 2.1.). This bug completely bypasses PKCE protection.

Reserved 2025-04-30 | Published 2025-05-01 | Updated 2025-05-01 | Assigner cloudflare

Problem types

CWE-287 Improper Authentication

Product status

Default status
unaffected

Any version before 0.0.5
affected

References

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

cve.org (CVE-2025-4144)

nvd.nist.gov (CVE-2025-4144)

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