function wphub_excerpt_meta_description() {
	if ( ! is_single() ) {
		return;
	}

	if ( ! has_excerpt() ) {
		return;
	}

	$excerpt = get_the_excerpt();
	?>
	<meta name="description" content="<?= esc_attr( $excerpt ) ?>" />
	<meta property="og:description" content="<?= esc_attr( $excerpt ) ?>" />
	<?php
}

add_action( 'wp_head', 'wphub_excerpt_meta_description' );