Why are available updates of CKeditor not visible in the update report in Drupal 7? /admin/reports/updates lists a few updates, but the ckeditor module is missing here. It runs in version 1.9, since then a few security updates have been released, but it does not matter how often I run the cron or update the list manually, the updates for ckeditor wont be listed here.

The module itself works perfectly fine. How come?
Drupal only check for drupal modules. The CKEditor module is https://www.drupal.org/project/ckeditor and the latest version is 7.x-1.16. This information should appear in admin/reports/updates.

I suppose you are talking about the CKEditor library which is not handled by the page admin/reports/updates.