Headline
GHSA-vh4h-fvqf-q9wv: Duplicate Advisory: @cloudflare/workers-oauth-provider PKCE bypass via downgrade attack
Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-qgp8-v765-qxx9. This link is maintained to preserve external references.
Original 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.
- GitHub Advisory Database
- GitHub Reviewed
- GHSA-vh4h-fvqf-q9wv
Duplicate Advisory: @cloudflare/workers-oauth-provider PKCE bypass via downgrade attack
Moderate severity GitHub Reviewed Published May 1, 2025 to the GitHub Advisory Database • Updated May 1, 2025
Withdrawn This advisory was withdrawn on May 1, 2025
Package
npm @cloudflare/workers-oauth-provider (npm)
Affected versions
< 0.0.5
Published by the National Vulnerability Database
May 1, 2025
Published to the GitHub Advisory Database
May 1, 2025