Certificate verification for the Nextcloud CalDAV server failed

[sharbich]

Hello,
i'm seeing an error message in the roundcube error.log indicating that I can't access my Nextcloud server.

[24-Feb-2026 17:47:36 +0000]: <26e51590> PHP Error: Unable to connect to tls://nextcloud.intern.example.com:443. Error: stream_socket_client(): Unable to connect to tls://nextcloud.intern.example.com:443 (Unknown error)
stream_socket_client(): Failed to enable crypto
stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages:
error:0A000086:SSL routines::certificate verify failed in /var/www/html/vendor/pear/http_request2/HTTP/Request2/SocketWrapper.php on line 135 (GET /?_task=calendar&source=__bdays__&_action=load_events&start=2026-02-23T00%3A00%3A00&end=2026-03-02T00%3A00%3A00&_=1771955256252)

My self-signed certificate cannot be verified. How can I resolve this issue? Here are my config.inc.php configuration:

root@62c6e2adb67e:/var/www/html# cat plugins/calendar/config.inc.php
<?php
$config['calendar_driver'] = "caldav";
$config['calendar_caldav_server'] = "https://nextcloud.intern.example.com/remote.php/dav";
$config['calendar_default_view'] = "agendaWeek";
$config['calendar_contact_birthdays'] = false;
$config['calendar_timeslots'] = 2;
$config['calendar_agenda_range'] = 60;
$config['calendar_first_day'] = 1;
$config['calendar_first_hour'] = 6;
$config['calendar_work_start'] = 6;
$config['calendar_work_end'] = 18;
$config['calendar_time_indicator'] = true;
$config['calendar_show_weekno'] = 0;
$config['calendar_default_alarm_type'] = '';
$config['calendar_default_alarm_offset'] = '-15M';
$config['calendar_event_coloring'] = 0;
$config['calendar_categories'] = [
  'Personal' => 'c0c0c0',
      'Work' => 'ff0000',
    'Family' => '00ff00',
   'Holiday' => 'ff6600',
];
$config['calendar_allow_invite_shared'] = false;
$config['calendar_allow_itip_uninvited'] = true;
$config['calendar_itip_send_option'] = 3;
$config['calendar_itip_after_action'] = 0;
$config['calendar_freebusy_trigger'] = false;
$config['calendar_include_freebusy_data'] = 1;
$config['calendar_itip_smtp_server'] = null;
$config['calendar_itip_smtp_user'] = 'smtpauth';
$config['calendar_itip_smtp_pass'] = '123456';
$config['kolab_invitation_calendars'] = false;
$config['calendar_caldav_url'] = 'https://nextcloud.intern.example.com/davical/caldav.php/%u/%n';;
$config['calendar_freebusy_session_auth_url'] = null;
$config['calendar_nextcloud_url'] = null;

Regards, Stefan Harbich

[alec]

Try this in the libkolab plugin config.

Code Select Expand

$config['kolab_http_request'] = [
    'ssl_verify_peer' => false,
    'ssl_verify_host' => false,
];


[sharbich]

Hi Alec,
thank you, my calendars are now being updated. However, the appointments are not showing up in the Roundcube calendar. I'm getting a database error. Could someone help me with this?

[25-Feb-2026 09:58:23 +0000]: <be2f74e4> PHP Error: Failed to write to kolab cache (POST /?_task=calendar&_action=refresh)
[25-Feb-2026 09:58:23 +0000]: <be2f74e4> DB Error: [7] FEHLER:  ungültige Eingabesyntax für Typ integer: »«
LINE 1: ... FROM "kolab_cache_dav_event" WHERE "folder_id" = '' AND "ch...
                                                             ^ (SQL Query: SELECT * FROM "kolab_cache_dav_event" WHERE "folder_id" = '' AND "changed" >= '2026-02-25 09:57:06' AND "dtstart" <= '2026-03-02 12:00:00' AND "dtend" >= '2026-02-22 12:00:00') in /var/www/html/program/lib/Roundcube/rcube_db.php on line 577 (POST /?_task=calendar&_action=refresh)