Index: src/wp-includes/capabilities.php
===================================================================
--- src/wp-includes/capabilities.php	(revision 46733)
+++ src/wp-includes/capabilities.php	(working copy)
@@ -241,6 +241,13 @@
 			}
 
 			$status_obj = get_post_status_object( $post->post_status );
+			if( !$status_obj ){
+				/* translators: 1: Post status, 2: Capability name. */
+				_doing_it_wrong( __FUNCTION__, sprintf( __( 'The post status %1$s is not registered, so it may not be reliable to check the capability "%2$s" against a post with that status.' ), $post->post_status, $cap ), '5.3.1' );
+				$caps[] = 'edit_others_posts';
+				break;
+			}
+
 			if ( $status_obj->public ) {
 				$caps[] = $post_type->cap->read;
 				break;
Index: src/wp-includes/class-wp-query.php
===================================================================
--- src/wp-includes/class-wp-query.php	(revision 46733)
+++ src/wp-includes/class-wp-query.php	(working copy)
@@ -3056,32 +3056,36 @@
 				$this->is_single     = true;
 				$this->is_attachment = true;
 			}
-			$post_status_obj = get_post_status_object( $status );
 
 			// If the post_status was specifically requested, let it pass through.
-			if ( ! $post_status_obj->public && ! in_array( $status, $q_status ) ) {
-
-				if ( ! is_user_logged_in() ) {
-					// User must be logged in to view unpublished posts.
-					$this->posts = array();
-				} else {
-					if ( $post_status_obj->protected ) {
-						// User must have edit permissions on the draft to preview.
-						if ( ! current_user_can( $edit_cap, $this->posts[0]->ID ) ) {
-							$this->posts = array();
+			if ( ! in_array( $status, $q_status ) ) {
+				$post_status_obj = get_post_status_object( $status );
+				if ( $post_status_obj && ! $post_status_obj->public ){
+					if ( ! is_user_logged_in() ) {
+						// User must be logged in to view unpublished posts.
+						$this->posts = array();
+					} else {
+						if ( $post_status_obj->protected ) {
+							// User must have edit permissions on the draft to preview.
+							if ( ! current_user_can( $edit_cap, $this->posts[0]->ID ) ) {
+								$this->posts = array();
+							} else {
+								$this->is_preview = true;
+								if ( 'future' != $status ) {
+									$this->posts[0]->post_date = current_time( 'mysql' );
+								}
+							}
+						} elseif ( $post_status_obj->private ) {
+							if ( ! current_user_can( $read_cap, $this->posts[0]->ID ) ) {
+								$this->posts = array();
+							}
 						} else {
-							$this->is_preview = true;
-							if ( 'future' != $status ) {
-								$this->posts[0]->post_date = current_time( 'mysql' );
-							}
-						}
-					} elseif ( $post_status_obj->private ) {
-						if ( ! current_user_can( $read_cap, $this->posts[0]->ID ) ) {
 							$this->posts = array();
 						}
-					} else {
-						$this->posts = array();
 					}
+				} else {
+					// Post status not registered, assume it's not public.
+					$this->posts = array();
 				}
 			}