Request header field sentry-trace is not allowed by Access-Control-Allow-Headers in preflight response

Question

I'm developing a Frontend using NextJS and Keycloak for auth-purpose. After adding Sentry, I'm facing this issue here, where the token endpoint of Keycloak is returning an error; So I can log in.

I've tried many things:

• Change the web-origin config of Keycloak, which (obviously) doesn't change or solves the problem
• Play with the Sentry client config, without success, because the denyUrls property still make the Sentry SDK send the sentry-trace into the request.

Now I don't have any more Idea, so I coming here for more help.

Answer 1

Unfortunately, Keycloak has hardcoded list of allowed headers, so you can't configure Keycloak for sentry-trace header.

You can have some non ideal work arounds:

• don't use sentry
• compile own hacked Keycloak version, where you allow that header
• add reverse proxy in front of Keycloak, which will add sentry-trace header to allowed headers
• ...