CVE-2026-55672 ZITADEL: Missing client_id binding in OIDC authorization code exchange and refresh token flows (RFC 6749 Section 4.1.3 violation)

ZITADEL is an open source identity management platform. Prior to 3.4.12 and 4.15.2, ZITADEL's OAuth2 and OIDC CodeExchange, RefreshToken, and device token flows fail to verify that the requesting client matches the client that initiated the authorization flow, allowing intercepted grants or refre...

ZITADEL: Missing client_id binding in OIDC authorization code exchange and refresh token flows (RFC 6749 Section 4.1.3 violation)

Summary Zitadel's OAuth2 / OIDC CodeExchange and RefreshToken implementations omit a critical validation step to ensure that the requesting client matches the client that originally initiated the authorization flow. This violates RFC 6749 Section 4.1.3, which mandates that the authorization serve...