diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-sites-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-sites-controller.php
index feb12673e951e..b3c547d84da25 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-sites-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-sites-controller.php
@@ -133,6 +133,16 @@ public function get_items_permissions_check( $request ) {
 			return $multisite_support;
 		}
 
+		foreach ( array( 'network', 'network_exclude' ) as $network_key ) {
+			if ( ! isset( $request[ $network_key ] ) ) {
+				continue;
+			}
+			$network_check = $this->check_network_ids( (array) $request[ $network_key ] );
+			if ( is_wp_error( $network_check ) ) {
+				return $network_check;
+			}
+		}
+
 		if ( $this->check_edit_permission() ) {
 			return true;
 		}
@@ -142,30 +152,6 @@ public function get_items_permissions_check( $request ) {
 			return true;
 		}
 
-		if ( isset( $request['network'] ) ) {
-			$network_check = $this->check_network_ids_exist( (array) $request['network'] );
-			if ( is_wp_error( $network_check ) ) {
-				return $network_check;
-			}
-
-			$network_access = $this->check_network_access( get_current_user_id(), (array) $request['network'] );
-			if ( is_wp_error( $network_access ) ) {
-				return $network_access;
-			}
-		}
-
-		if ( isset( $request['network_exclude'] ) ) {
-			$network_check = $this->check_network_ids_exist( (array) $request['network_exclude'] );
-			if ( is_wp_error( $network_check ) ) {
-				return $network_check;
-			}
-
-			$network_access = $this->check_network_access( get_current_user_id(), (array) $request['network_exclude'] );
-			if ( is_wp_error( $network_access ) ) {
-				return $network_access;
-			}
-		}
-
 		return new WP_Error( 'rest_forbidden_context', __( 'Sorry, you are not allowed to view sites.' ), array( 'status' => rest_authorization_required_code() ) );
 	}
 
@@ -436,15 +422,10 @@ public function get_item_permissions_check( $request ) {
 		}
 
 		if ( $site->network_id > 0 ) {
-			$network_check = $this->check_network_ids_exist( (array) $site->network_id );
+			$network_check = $this->check_network_ids( (array) $site->network_id );
 			if ( is_wp_error( $network_check ) ) {
 				return $network_check;
 			}
-
-			$network_access = $this->check_network_access( get_current_user_id(), (array) $site->network_id );
-			if ( is_wp_error( $network_access ) ) {
-				return $network_access;
-			}
 		}
 
 		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
@@ -461,37 +442,27 @@ public function get_item_permissions_check( $request ) {
 	}
 
 	/**
-	 * Validates that all network IDs in a request parameter exist.
+	 * Validates that the given network IDs exist and are accessible to the current user.
+	 *
+	 * A user can always access the current network. Access to any other
+	 * network requires the user to be a super admin of that network.
 	 *
 	 * @since 7.2.0
 	 *
 	 * @param int[] $network_ids Array of network IDs.
-	 * @return true|WP_Error True if all network IDs are valid, WP_Error otherwise.
+	 * @return true|WP_Error True if all network IDs exist and are accessible, WP_Error otherwise.
 	 */
-	protected function check_network_ids_exist( array $network_ids ) {
+	protected function check_network_ids( array $network_ids ) {
+		$current_network_id = get_current_network_id();
+		$user_id            = get_current_user_id();
+
+		_prime_network_caches( $network_ids );
 		foreach ( $network_ids as $network_id ) {
 			if ( ! get_network( $network_id ) ) {
 				return new WP_Error( 'rest_network_id_invalid', __( 'Invalid network ID.' ), array( 'status' => 400 ) );
 			}
 		}
 
-		return true;
-	}
-
-	/**
-	 * Checks if a user can access sites on the given networks.
-	 *
-	 * A user can always access the current network. Access to any other
-	 * network requires the user to be a super admin of that network.
-	 *
-	 * @since 7.2.0
-	 *
-	 * @param int   $user_id     User ID.
-	 * @param int[] $network_ids Array of network IDs.
-	 * @return true|WP_Error True if the user can access all given networks, WP_Error otherwise.
-	 */
-	protected function check_network_access( $user_id, array $network_ids ) {
-		$current_network_id = get_current_network_id();
 		if ( count( $network_ids ) === 1 && $current_network_id === $network_ids[0] ) {
 			return true;
 		}
@@ -545,15 +516,10 @@ public function create_item_permissions_check( $request ) {
 
 		$network_id = isset( $request['network'] ) ? (int) $request['network'] : get_current_network_id();
 		if ( $network_id > 0 ) {
-			$network_check = $this->check_network_ids_exist( (array) $network_id );
+			$network_check = $this->check_network_ids( (array) $network_id );
 			if ( is_wp_error( $network_check ) ) {
 				return $network_check;
 			}
-
-			$network_access = $this->check_network_access( get_current_user_id(), (array) $network_id );
-			if ( is_wp_error( $network_access ) ) {
-				return $network_access;
-			}
 		}
 
 		if ( ! current_user_can( 'create_sites' ) ) {
@@ -683,15 +649,10 @@ public function update_item_permissions_check( $request ) {
 
 		$network_id = isset( $request['network'] ) ? (int) $request['network'] : $site->network_id;
 		if ( $network_id > 0 ) {
-			$network_check = $this->check_network_ids_exist( (array) $network_id );
+			$network_check = $this->check_network_ids( (array) $network_id );
 			if ( is_wp_error( $network_check ) ) {
 				return $network_check;
 			}
-
-			$network_access = $this->check_network_access( get_current_user_id(), (array) $network_id );
-			if ( is_wp_error( $network_access ) ) {
-				return $network_access;
-			}
 		}
 
 		if ( ! $this->check_edit_permission() ) {
@@ -789,6 +750,13 @@ public function delete_item_permissions_check( $request ) {
 			return $site;
 		}
 
+		if ( $site->network_id > 0 ) {
+			$network_check = $this->check_network_ids( (array) $site->network_id );
+			if ( is_wp_error( $network_check ) ) {
+				return $network_check;
+			}
+		}
+
 		if ( ! $this->check_delete_permission( $site ) ) {
 			return new WP_Error( 'rest_cannot_delete', __( 'Sorry, you are not allowed to delete this site.' ), array( 'status' => rest_authorization_required_code() ) );
 		}
diff --git a/tests/phpunit/tests/rest-api/wpRestSitesController.php b/tests/phpunit/tests/rest-api/wpRestSitesController.php
index 3a0e02b286734..753f1a6f79180 100644
--- a/tests/phpunit/tests/rest-api/wpRestSitesController.php
+++ b/tests/phpunit/tests/rest-api/wpRestSitesController.php
@@ -1999,7 +1999,7 @@ public function test_get_items_filter_with_includes_user() {
 	/**
 	 * @ticket 40365
 	 * @covers ::get_items_permissions_check
-	 * @covers ::check_network_ids_exist
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_items_permissions_check_invalid_network_id() {
@@ -2015,7 +2015,7 @@ public function test_get_items_permissions_check_invalid_network_id() {
 	/**
 	 * @ticket 40365
 	 * @covers ::get_items_permissions_check
-	 * @covers ::check_network_ids_exist
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_items_permissions_check_invalid_network_exclude_id() {
@@ -2031,7 +2031,7 @@ public function test_get_items_permissions_check_invalid_network_exclude_id() {
 	/**
 	 * @ticket 40365
 	 * @covers ::get_items_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_items_permissions_check_denies_access_to_another_network() {
@@ -2048,7 +2048,7 @@ public function test_get_items_permissions_check_denies_access_to_another_networ
 	/**
 	 * @ticket 40365
 	 * @covers ::get_items_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_items_permissions_check_allows_filtering_by_the_current_network() {
@@ -2066,7 +2066,7 @@ public function test_get_items_permissions_check_allows_filtering_by_the_current
 	/**
 	 * @ticket 40365
 	 * @covers ::create_item_permissions_check
-	 * @covers ::check_network_ids_exist
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_create_item_permissions_check_invalid_network_id() {
@@ -2084,7 +2084,7 @@ public function test_create_item_permissions_check_invalid_network_id() {
 	/**
 	 * @ticket 40365
 	 * @covers ::create_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_create_item_permissions_check_denies_access_to_another_network() {
@@ -2103,7 +2103,7 @@ public function test_create_item_permissions_check_denies_access_to_another_netw
 	/**
 	 * @ticket 40365
 	 * @covers ::create_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_create_item_permissions_check_allows_a_super_admin_of_the_target_network() {
@@ -2123,7 +2123,7 @@ public function test_create_item_permissions_check_allows_a_super_admin_of_the_t
 	/**
 	 * @ticket 40365
 	 * @covers ::update_item_permissions_check
-	 * @covers ::check_network_ids_exist
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_update_item_permissions_check_invalid_network_id() {
@@ -2141,7 +2141,7 @@ public function test_update_item_permissions_check_invalid_network_id() {
 	/**
 	 * @ticket 40365
 	 * @covers ::update_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_update_item_permissions_check_denies_moving_a_site_to_another_network() {
@@ -2161,7 +2161,7 @@ public function test_update_item_permissions_check_denies_moving_a_site_to_anoth
 	/**
 	 * @ticket 40365
 	 * @covers ::update_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_update_item_permissions_check_allows_the_sites_own_network_by_default() {
@@ -2175,10 +2175,73 @@ public function test_update_item_permissions_check_allows_the_sites_own_network_
 		$this->assertEquals( 200, $response->get_status() );
 	}
 
+	/**
+	 * @ticket 40365
+	 * @covers ::delete_item_permissions_check
+	 * @covers ::check_network_ids
+	 * @group ms-required
+	 */
+	public function test_delete_item_permissions_check_invalid_network_id() {
+		$blog_id = self::factory()->blog->create();
+
+		// Orphan the site from its network to simulate an invalid stored network ID.
+		wp_update_site( $blog_id, array( 'network_id' => REST_TESTS_IMPOSSIBLY_HIGH_NUMBER ) );
+
+		wp_set_current_user( self::$superadmin_id );
+
+		$request = new WP_REST_Request( 'DELETE', '/wp/v2/sites/' . $blog_id );
+		$request->set_param( 'id', $blog_id );
+
+		$response = rest_get_server()->dispatch( $request );
+		$this->assertErrorResponse( 'rest_network_id_invalid', $response, 400 );
+	}
+
+	/**
+	 * @ticket 40365
+	 * @covers ::delete_item_permissions_check
+	 * @covers ::check_network_ids
+	 * @group ms-required
+	 */
+	public function test_delete_item_permissions_check_denies_access_to_another_network() {
+		$network_id = self::factory()->network->create();
+		delete_network_option( $network_id, 'site_admins' );
+		$blog_id = self::factory()->blog->create( array( 'site_id' => $network_id ) );
+
+		wp_set_current_user( self::$superadmin_id );
+
+		$request = new WP_REST_Request( 'DELETE', '/wp/v2/sites/' . $blog_id );
+		$request->set_param( 'id', $blog_id );
+
+		$response = rest_get_server()->dispatch( $request );
+		$this->assertErrorResponse( 'rest_cannot_view_network', $response, 403 );
+	}
+
+	/**
+	 * @ticket 40365
+	 * @covers ::delete_item_permissions_check
+	 * @covers ::check_network_ids
+	 * @group ms-required
+	 */
+	public function test_delete_item_permissions_check_allows_a_super_admin_of_the_sites_network() {
+		$network_id = self::factory()->network->create();
+		$user       = self::factory()->user->create_and_get();
+		update_network_option( $network_id, 'site_admins', array( $user->user_login ) );
+		// delete_sites is checked against the current network, so grant it there too.
+		grant_super_admin( $user->ID );
+		$blog_id = self::factory()->blog->create( array( 'site_id' => $network_id ) );
+
+		wp_set_current_user( $user->ID );
+
+		$request = new WP_REST_Request( 'DELETE', '/wp/v2/sites/' . $blog_id );
+		$request->set_param( 'id', $blog_id );
+
+		$this->assertTrue( $this->endpoint->delete_item_permissions_check( $request ) );
+	}
+
 	/**
 	 * @ticket 40365
 	 * @covers ::get_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_item_permissions_check_denies_a_site_on_another_network() {
@@ -2199,7 +2262,7 @@ public function test_get_item_permissions_check_denies_a_site_on_another_network
 	/**
 	 * @ticket 40365
 	 * @covers ::get_item_permissions_check
-	 * @covers ::check_network_access
+	 * @covers ::check_network_ids
 	 * @group ms-required
 	 */
 	public function test_get_item_permissions_check_allows_a_site_on_the_current_network() {
diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index f54dfc053279d..85cd6b8785df3 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -22,13 +22,7 @@ mockedApiResponse.Schema = {
         "wp-block-editor/v1",
         "wp-abilities/v1"
     ],
-    "authentication": {
-        "application-passwords": {
-            "endpoints": {
-                "authorization": "http://example.org/wp-admin/authorize-application.php"
-            }
-        }
-    },
+    "authentication": [],
     "routes": {
         "/": {
             "namespace": "",
@@ -11209,7 +11203,6 @@ mockedApiResponse.Schema = {
                             "required": false
                         },
                         "network": {
-                            "default": 1,
                             "description": "The site's network ID. Default is the current network ID.",
                             "type": "integer",
                             "required": false