Executive brief
MCPHub is an open-source platform that includes an embedded OAuth 2.0 authorization server for identity management. Before version 1.0.32, the authorization server disables client authentication by default and makes PKCE enforcement optional, allowing attackers who intercept an authorization code to redeem it for access tokens without providing credentials. This could lead to unauthorized account access and privilege escalation.
Technical details
The vulnerability is an authentication bypass in MCPHub's embedded OAuth 2.0 authorization server. The root cause is that client authentication is disabled by default and PKCE (Proof Key for Code Exchange) enforcement is optional. An attacker who obtains an authorization code through network interception can exchange it for access tokens at the token endpoint without presenting a client secret or valid PKCE verifier. This affects the OAuth token exchange flow and requires only network access and code interception. The fix (version 1.0.32+) enforces mandatory client authentication for confidential clients and requires S256-only PKCE for public clients.
Affected products
- samanhappy MCPHub before 1.0.32
Timeline
- 2026-09-12: disclosed
- 2026-08-23: patched: Fix committed to repository