Dapr - OIDC Discovery Issuer and JWKS URI Injection via Unvalidated X-Forwarded-Host

Summary

Dapr Sentry's OIDC discovery endpoint derives the issuer and jwks_uri of the /.well-known/openid-configuration document from the request Host, honoring an attacker-controlled X-Forwarded-Host header without validation when no allowed-hosts list is configured (the default), and serves the document with a one-hour public cache lifetime. A remote unauthenticated attacker can poison the discovery document so relying parties performing dynamic (unpinned) discovery fetch the JWKS from an attacker-controlled server, causing attacker-signed JWTs to be accepted. Exploitation requires the OIDC server enabled without a configured jwt-issuer or oidc-allowed-hosts.