Security context

Highlights

Auth Bypass: 38 prior fixes. Scrutinize any change in this area.

src/fastmcp/server/auth/oauth_proxy.py: most-fixed (7 issues). Treat as high-risk during review.

43 high-severity fixes in this history; regressions here are high-impact.

Recurring patterns

Auth Bypass: Asynchronous authorization check callables were previously treated implicitly as truthy coroutine objects rather than being awaited, allowing critical access checks to be bypassed completely. In addition, raw component getters sometimes bypassed high-level authorization controls.

Auth Bypass: Azure token verification was vulnerable to scope validation bypasses when receiving empty or OIDC-only scopes, and was susceptible to cross-application token reuse because it validated incoming tokens against a global endpoint like Microsoft Graph instead of verifying the specific application client_id.

Auth Bypass: The JWT verifier was vulnerable to signature validation bypass via public key confusion when receiving symmetric HS* algorithms while configured with asymmetric keys (PEM or JWKS URIs), and failed to reject unsupported critical headers when strict header checking was disabled.