diff --git a/wp-admin/includes/network.php b/wp-admin/includes/network.php
index 67a9e0289e..9577172a80 100644
--- a/wp-admin/includes/network.php
+++ b/wp-admin/includes/network.php
@@ -148,26 +148,8 @@ function network_step1( $errors = false ) {
 		die();
 	}
 
-	$hostname  = get_clean_basedomain();
-	$has_ports = strstr( $hostname, ':' );
-	if ( ( false !== $has_ports && ! in_array( $has_ports, array( ':80', ':443' ), true ) ) ) {
-		wp_admin_notice(
-			'<strong>' . __( 'Error:' ) . '</strong> ' . __( 'You cannot install a network of sites with your server address.' ),
-			array(
-				'additional_classes' => array( 'error' ),
-			)
-		);
-
-		echo '<p>' . sprintf(
-			/* translators: %s: Port number. */
-			__( 'You cannot use port numbers such as %s.' ),
-			'<code>' . $has_ports . '</code>'
-		) . '</p>';
-		echo '<a href="' . esc_url( admin_url() ) . '">' . __( 'Go to Dashboard' ) . '</a>';
-		echo '</div>';
-		require_once ABSPATH . 'wp-admin/admin-footer.php';
-		die();
-	}
+	// Strip standard port from hostname.
+	$hostname = preg_replace( '/(?::80|:443)$/', '', get_clean_basedomain() );
 
 	echo '<form method="post">';
 
diff --git a/wp-admin/network/site-info.php b/wp-admin/network/site-info.php
index defcc26e44..46f67cced5 100644
--- a/wp-admin/network/site-info.php
+++ b/wp-admin/network/site-info.php
@@ -66,8 +66,14 @@ if ( isset( $_REQUEST['action'] ) && 'update-site' === $_REQUEST['action'] ) {
 		}
 
 		$blog_data['scheme'] = $update_parsed_url['scheme'];
+
+		// Make sure to not lose the port if it was provided.
 		$blog_data['domain'] = $update_parsed_url['host'];
-		$blog_data['path']   = $update_parsed_url['path'];
+		if ( isset( $update_parsed_url['port'] ) ) {
+			$blog_data['domain'] .= ':' . $update_parsed_url['port'];
+		}
+
+		$blog_data['path'] = $update_parsed_url['path'];
 	}
 
 	$existing_details     = get_site( $id );
@@ -88,16 +94,18 @@ if ( isset( $_REQUEST['action'] ) && 'update-site' === $_REQUEST['action'] ) {
 
 	$old_home_url    = trailingslashit( esc_url( get_option( 'home' ) ) );
 	$old_home_parsed = parse_url( $old_home_url );
+	$old_home_host   = $old_home_parsed['host'] . ( isset( $old_home_parsed['port'] ) ? ':' . $old_home_parsed['port'] : '' );
 
-	if ( $old_home_parsed['host'] === $existing_details->domain && $old_home_parsed['path'] === $existing_details->path ) {
+	if ( $old_home_host === $existing_details->domain && $old_home_parsed['path'] === $existing_details->path ) {
 		$new_home_url = untrailingslashit( sanitize_url( $blog_data['scheme'] . '://' . $new_details->domain . $new_details->path ) );
 		update_option( 'home', $new_home_url );
 	}
 
 	$old_site_url    = trailingslashit( esc_url( get_option( 'siteurl' ) ) );
 	$old_site_parsed = parse_url( $old_site_url );
+	$old_site_host   = $old_site_parsed['host'] . ( isset( $old_site_parsed['port'] ) ? ':' . $old_site_parsed['port'] : '' );
 
-	if ( $old_site_parsed['host'] === $existing_details->domain && $old_site_parsed['path'] === $existing_details->path ) {
+	if ( $old_site_host === $existing_details->domain && $old_site_parsed['path'] === $existing_details->path ) {
 		$new_site_url = untrailingslashit( sanitize_url( $blog_data['scheme'] . '://' . $new_details->domain . $new_details->path ) );
 		update_option( 'siteurl', $new_site_url );
 	}
diff --git a/wp-includes/embed.php b/wp-includes/embed.php
index 6c767cfcab..915314a767 100644
--- a/wp-includes/embed.php
+++ b/wp-includes/embed.php
@@ -627,12 +627,13 @@ function get_oembed_response_data_for_url( $url, $args ) {
 			wp_parse_url( $url ),
 			array(
 				'host' => '',
+				'port' => null,
 				'path' => '/',
 			)
 		);
 
 		$qv = array(
-			'domain'                 => $url_parts['host'],
+			'domain'                 => $url_parts['host'] . ( $url_parts['port'] ? ':' . $url_parts['port'] : '' ),
 			'path'                   => '/',
 			'update_site_meta_cache' => false,
 		);
diff --git a/wp-includes/feed.php b/wp-includes/feed.php
index 4532697ea5..ec7c3ca9a9 100644
--- a/wp-includes/feed.php
+++ b/wp-includes/feed.php
@@ -660,8 +660,14 @@ function rss2_site_icon() {
  * @return string Correct link for the atom:self element.
  */
 function get_self_link() {
-	$host = parse_url( home_url() );
-	return set_url_scheme( 'http://' . $host['host'] . wp_unslash( $_SERVER['REQUEST_URI'] ) );
+	$parsed = parse_url( home_url() );
+
+	$domain = $parsed['host'];
+	if ( isset( $parsed['port'] ) ) {
+		$domain .= ':' . $parsed['port'];
+	}
+
+	return set_url_scheme( 'http://' . $domain . wp_unslash( $_SERVER['REQUEST_URI'] ) );
 }
 
 /**
diff --git a/wp-includes/media.php b/wp-includes/media.php
index b360c6dd34..76fb2b63c7 100644
--- a/wp-includes/media.php
+++ b/wp-includes/media.php
@@ -1363,8 +1363,17 @@ function wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attac
 	 * If currently on HTTPS, prefer HTTPS URLs when we know they're supported by the domain
 	 * (which is to say, when they share the domain name of the current request).
 	 */
-	if ( is_ssl() && ! str_starts_with( $image_baseurl, 'https' ) && parse_url( $image_baseurl, PHP_URL_HOST ) === $_SERVER['HTTP_HOST'] ) {
-		$image_baseurl = set_url_scheme( $image_baseurl, 'https' );
+	if ( is_ssl() && ! str_starts_with( $image_baseurl, 'https' ) ) {
+		// Since the `Host:` header might contain a port we should
+		// compare it against the image URL using the same port.
+		$parsed = parse_url( $image_baseurl );
+		$domain = $parsed['host'];
+		if ( isset( $parsed['port'] ) ) {
+			$domain .= ':' . $parsed['port'];
+		}
+		if ( $_SERVER['HTTP_HOST'] === $domain ) {
+			$image_baseurl = set_url_scheme( $image_baseurl, 'https' );
+		}
 	}
 
 	/*
diff --git a/wp-includes/ms-site.php b/wp-includes/ms-site.php
index 65e7d8d78d..6e19758790 100644
--- a/wp-includes/ms-site.php
+++ b/wp-includes/ms-site.php
@@ -524,11 +524,7 @@ function wp_prepare_site_data( $data, $defaults, $old_site = null ) {
 function wp_normalize_site_data( $data ) {
 	// Sanitize domain if passed.
 	if ( array_key_exists( 'domain', $data ) ) {
-		$data['domain'] = trim( $data['domain'] );
-		$data['domain'] = preg_replace( '/\s+/', '', sanitize_user( $data['domain'], true ) );
-		if ( is_subdomain_install() ) {
-			$data['domain'] = str_replace( '@', '', $data['domain'] );
-		}
+		$data['domain'] = preg_replace( '/[^a-z0-9\-.:]+/i', '', $data['domain'] );
 	}
 
 	// Sanitize path if passed.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index d401253c50..491205e70c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58096';
+$wp_version = '6.6-alpha-58097';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.