Automatic updates no longer work with via SSH2 from WP 6.6

[srfg]

Since WordPress 6.6, automatic updates (core, plugins) no longer work via an SSH connection. All updates work normally if you trigger them manually.

Environment:

• PHP 8.2
• WordPress 6.6 and later (including 6.6.2)

Affected instances

• Clean installation of WordPress and 70 other websites that we run. So we can reproduce the problem.

We do not receive any information in the log file. To get more information, we used the "Easy Updates Manager plugin. It does not work either and we received the following error:

[16-Oct-2024 13:39:21 UTC] PHP Fatal error: Uncaught TypeError: ftp_nlist(): Argument #1 ($ftp) must be of type FTP\Connection, null given in /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ftpext.php:438

Stack trace:
#0 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ftpext.php(438): ftp_nlist()
#1 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-base.php(231): WP_Filesystem_FTPext->exists()
#2 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-base.php(58): WP_Filesystem_Base->find_folder()
#3 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-upgrader.php(997): WP_Filesystem_Base->abspath()
#4 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-automatic-updater.php(474): WP_Upgrader->maintenance_mode()
#5 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-automatic-updater.php(676): WP_Automatic_Updater->update()
#6 /var/www/https/***.***.at/wp/wp-includes/update.php(855): WP_Automatic_Updater->run()
#7 /var/www/https/***.***.at/wp/wp-content/plugins/stops-core-theme-and-plugin-updates/includes/MPSUM_Admin_Ajax.php(1057): wp_maybe_auto_update()
#8 /var/www/https/***.***.at/wp/wp-content/plugins/stops-core-theme-and-plugin-updates/includes/MPSUM_Admin_Ajax.php(144): MPSUM_Admin_Ajax->force_updates()
#9 /var/www/https/***.***.at/wp/wp-includes/class-wp-hook.php(324): MPSUM_Admin_Ajax->ajax_handler()
#10 /var/www/https/***.***.at/wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 11 /var/www/https/***.***.at/wp/wp-includes/plugin.php(517): WP_Hook->do_action()
#12 /var/www/https/***.***.at/wp/wp-admin/admin-ajax.php(192): do_action()
#13 {main} thrown in /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ftpext.php on line 438

A value is obviously missing. If we use the setting define('FS_METHOD', 'ssh2');, there is another fatal error:

[16-Oct-2024 15:41:54 UTC] Automatic updates starting...
[16-Oct-2024 15:41:54 UTC]   Automatic plugin updates starting...
[16-Oct-2024 15:41:54 UTC]     Upgrading plugin 'better-search-replace'...
[16-Oct-2024 15:41:54 UTC] PHP Fatal error:  Uncaught TypeError: ssh2_sftp_realpath(): Argument #1 ($sftp) must be of type resource, null given in /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ssh2.php:304

Stack trace:
#0 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ssh2.php(304): ssh2_sftp_realpath()
#1 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-base.php(261): WP_Filesystem_SSH2->cwd()
#2 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-base.php(238): WP_Filesystem_Base->search_for_folder()
#3 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-base.php(58): WP_Filesystem_Base->find_folder()
#4 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-upgrader.php(997): WP_Filesystem_Base->abspath()
#5 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-automatic-updater.php(474): WP_Upgrader->maintenance_mode()
#6 /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-automatic-updater.php(676): WP_Automatic_Updater->update()
#7 /var/www/https/***.***.at/wp/wp-includes/update.php(855): WP_Automatic_Updater->run()
#8 /var/www/https/***.***.at/wp/wp-content/plugins/stops-core-theme-and-plugin-updates/includes/MPSUM_Admin_Ajax.php(1057): wp_maybe_auto_update()
#9 /var/www/https/***.***.at/wp/wp-content/plugins/stops-core-theme-and-plugin-updates/includes/MPSUM_Admin_Ajax.php(144): MPSUM_Admin_Ajax->force_updates()
#10 /var/www/https/***.***.at/wp/wp-includes/class-wp-hook.php(324): MPSUM_Admin_Ajax->ajax_handler()
#11 /var/www/https/***.***.at/wp/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#12 /var/www/https/***.***.at/wp/wp-includes/plugin.php(517): WP_Hook->do_action()
#13 /var/www/https/***.***.at/wp/wp-admin/admin-ajax.php(192): do_action()
#14 {main}
  thrown in /var/www/https/***.***.at/wp/wp-admin/includes/class-wp-filesystem-ssh2.php on line 304

Configuration:

define(‘FTP_METHOD’,’ssh2′); 
define(‘FTP_PUBKEY’,’/xxx/xxx/xxx.xx’);
define(‘FTP_PRIKEY’,’/xxx/xxx/xxx.xx’);
define(‘FTP_USER’,’xxxxxxxx’);
define(‘FTP_PASS’,”);
define(‘FTP_HOST’,’127.0.0.1:22′);

There is no problem with the direct method.