From a911c9523b7f30cb7d381d18c1ac16cc08016cfe Mon Sep 17 00:00:00 2001
From: Khokan Sardar <itzmekhokan@gmail.com>
Date: Thu, 20 Aug 2026 07:56:59 +0530
Subject: [PATCH] Upgrade/Install: Load the `.maintenance` file non-fatally.

`wp_is_maintenance_mode()` and `WP_Automatic_Updater::has_fatal_error()`
both check for `.maintenance` with `file_exists()` and then load it with
`require`. An update running in a concurrent request can delete the file
between the two, and with `opcache.enable_file_override=1` the cached
script entry keeps `file_exists()` returning true after the deletion, so
`require` fails and terminates the request.

Load the file with `include` and bail when it returns false, so a file
that disappears or becomes unreadable between the check and the load
leaves maintenance mode off instead of ending the request.

Fixes #65911.
---
 .../includes/class-wp-automatic-updater.php   |  7 ++--
 src/wp-includes/load.php                      |  8 ++++-
 .../tests/load/wpIsMaintenanceMode.php        | 34 +++++++++++++++++++
 3 files changed, 46 insertions(+), 3 deletions(-)
 create mode 100644 tests/phpunit/tests/load/wpIsMaintenanceMode.php

diff --git a/src/wp-admin/includes/class-wp-automatic-updater.php b/src/wp-admin/includes/class-wp-automatic-updater.php
index cd9426c6ef88b..fd094f0341231 100644
--- a/src/wp-admin/includes/class-wp-automatic-updater.php
+++ b/src/wp-admin/includes/class-wp-automatic-updater.php
@@ -1766,8 +1766,11 @@ protected function has_fatal_error() {
 			return false;
 		}
 
-		require $maintenance_file;
-		if ( ! is_int( $upgrading ) ) {
+		// The file may be removed between the check above and the load below.
+		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Warning emitted in expected failure case.
+		$maintenance_file_loaded = @include $maintenance_file;
+
+		if ( false === $maintenance_file_loaded || ! is_int( $upgrading ) ) {
 			return false;
 		}
 
diff --git a/src/wp-includes/load.php b/src/wp-includes/load.php
index 27c58b57dd671..bcab88242f3a3 100644
--- a/src/wp-includes/load.php
+++ b/src/wp-includes/load.php
@@ -441,7 +441,13 @@ function wp_is_maintenance_mode() {
 		return false;
 	}
 
-	require ABSPATH . '.maintenance';
+	// The file may be removed between the check above and the load below.
+	// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Warning emitted in expected failure case.
+	$maintenance_file_loaded = @include ABSPATH . '.maintenance';
+
+	if ( false === $maintenance_file_loaded ) {
+		return false;
+	}
 
 	// If the $upgrading timestamp is older than 10 minutes, consider maintenance over.
 	if ( ( time() - $upgrading ) >= 10 * MINUTE_IN_SECONDS ) {
diff --git a/tests/phpunit/tests/load/wpIsMaintenanceMode.php b/tests/phpunit/tests/load/wpIsMaintenanceMode.php
new file mode 100644
index 0000000000000..a8b66e5aa8e01
--- /dev/null
+++ b/tests/phpunit/tests/load/wpIsMaintenanceMode.php
@@ -0,0 +1,34 @@
+<?php
+/**
+ * Unit tests for `wp_is_maintenance_mode()`.
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ *
+ * @group load
+ *
+ * @covers ::wp_is_maintenance_mode
+ */
+class Test_WP_Is_Maintenance_Mode extends WP_UnitTestCase {
+
+	public function tear_down() {
+		if ( is_dir( ABSPATH . '.maintenance' ) ) {
+			rmdir( ABSPATH . '.maintenance' );
+		}
+
+		parent::tear_down();
+	}
+
+	/**
+	 * @ticket 65911
+	 */
+	public function test_should_return_false_when_the_maintenance_file_cannot_be_loaded() {
+		if ( file_exists( ABSPATH . '.maintenance' ) ) {
+			$this->markTestSkipped( 'A .maintenance file already exists in ABSPATH.' );
+		}
+
+		mkdir( ABSPATH . '.maintenance' );
+
+		$this->assertFalse( wp_is_maintenance_mode() );
+	}
+}