This is in connection to drupal.org issue #432384.
That's when I happen to request for page "node/1/aaa/bbbb", I'm served the response for "node/1" (it's parent page).
I can understand, this is the way Drupal menu system has been designed and works for some obvious reasons.
But I'm in a need to change this. Reason we have some aliased urls across the site, links from third party sites are taking (visitors and crawlers) to not existing page for which ideally http 404 response code and page not found to be returned. Instead Drupal showing it's parent page (with http res. code 200). This is leading to duplicate page in Google webmasters and misleading our genuine users.
I have found a patch to this issue. However it is working fine only for 80% of cases, some valid urls (admin/*, sites/default/files/ * , system/ajax/*, etc.,) leads to 404 page.
Would like to hear how others are dealing with this duplicate content issue concerning SEO and possible fix!