[CVE-2020-1955] Apache CouchDB Remote Privilege Escalation

[Jan Lehnardt <ja...@apache.org>]

Description
===========

CouchDB version 3.0.0 shipped with a new configuration setting that
governs access control to the entire database server called
`require_valid_user_except_for_up`. It was meant as an extension to the
long-standing setting `require_valid_user`, which in turn requires that
any and all requests to CouchDB will have to be made with valid
credentials, effectively forbidding any anonymous requests.

The new `require_valid_user_except_for_up` is an off-by-default setting
that was meant to allow requiring valid credentials for all endpoints
except for the `/_up` endpoint.

However, the implementation of this made an error that lead to not
enforcing credentials on any endpoint, when enabled.

CouchDB versions 3.0.1[1] and 3.1.0[2] fix this issue.

Mitigation
==========

Users who have not enabled `require_valid_user_except_for_up` are not
affected.

Users who have it enabled can either disable it again, or upgrade to
CouchDB versions 3.0.1[1] and 3.1.0[2].

[1]: https://docs.couchdb.org/en/stable/whatsnew/3.0.html#version-3-0-1
[2]: https://docs.couchdb.org/en/stable/whatsnew/3.1.html#version-3-1-0

On behalf of the CouchDB Security Team,
Jan Lehnardt
—