500 Internal Server Error: OAuth2 Authorization Endpoint Failed

Membrane API Gateway returns 500 Internal Server Error when the authorization endpoint of its OAuth2 authorization server (oauth2authserver) throws an unexpected exception while processing an authorization request.

The Error Response

The response contains the status 500 Internal Server Error and the problem type https://membrane-api.io/problems/internal. The type internal means that the gateway failed while processing the exchange. For this error, Membrane always suppresses the details, even in development mode, so the response does not contain a detail or a link to this page.

Which Requests Lead to This Error

The authorization endpoint (/oauth2/auth) validates the authorization request. Problems such as a missing client_id, an unknown client or an invalid scope are answered with regular OAuth2 error responses. This error covers unexpected failures beyond that validation.

Common Causes

A Parameter Appears Twice

The query string contains the same parameter more than once, for example scope twice. The parameter parser rejects duplicate keys.

Invalid Encoding

The query string contains an invalid percent-encoding, or the request URI cannot be parsed.

An Unexpected Failure in the Authorization Server

A failure in the session manager or elsewhere in the authorization server. This is rare and usually indicates a bug in Membrane.

How to Fix It

1. Client side: send every OAuth2 parameter once and percent-encode parameter values correctly.
2. Gateway operator: check the gateway log. Membrane logs the full exception at error level.
3. If the request was well-formed, report the problem with the stack trace on GitHub Issues.

No Details in Any Mode

Unlike most Membrane errors, this one never contains the detail or the link to this page, not even in development mode. Use the gateway log to find the cause.

Related Documentation

Configuration reference:

• oauth2authserver

Tutorials with runnable examples:

• OAuth2 Basics
• OAuth2 Client Credentials
• OAuth2 Password Flow

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