Roundcube/Horde webmail and websites on FastCGI are not accessible: Connection reset by peer: mod_fcgid: error reading data from FastCGI server

Symptoms

• Webmail:

  • Roundcube/Horde webmail shows the following error message in a web browser:

    Service Temporarily Unavailable
    The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.
    Apache Server at webmail.example.com Port 80

    ---

    500 external Server Error

  • The following messages appear in /var/log/psa-horde/psa-horde.log or /var/log/apache2/error.log:

    [warn] [client 203.0.113.2] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server
    [error] [client 203.0.113.2] Premature end of script headers: index.php

  • The following error messages may appear in /var/log/httpd/suexec_log:

    uid: (10021/horde_sysuser) gid: (510/510) cmd: cgi_wrapper
    target uid/gid (10021/510 or 504) mismatch with directory (0/503) or program (0/0)
    uid: (2523/horde_sysuser) gid: (2521/2521) cmd: cgi_wrapper
    directory is writable by others: (/var/www/cgi-bin/cgi_wrapper)

    ---

    uid: (996/roundcube_sysuser) gid: (1006/1006) cmd: cgi_wrapper
    file has no execute permission: (/var/www/cgi-bin/cgi_wrapper/cgi_wrapper)

• Websites on FastCGI:

  • Websites served by the PHP FastCGI handler are not loading with a 500 error. After changing a PHP handler to PHP-FPM, websites start to work.

  • CGI scripts do not work on a website.

  • Following error messages in /var/www/vhosts/system/example.com/logs/error_log:

    [warn] [client 203.0.113.2] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server
    [error] [client 203.0.113.2] Premature end of script headers: index.php

• Plesk migration:

  • The following warning appears during a Plesk migration:

    WARNING:()The webmail service horde is unavailable. It will be replaced with <webmail> for the following objects: <list of domains>

Cause

Permissions on the file /var/www/cgi-bin/cgi_wrapper are incorrect.

Resolution

1. Connect to the server via SSH

2. Correct the permissions:

   # chown root:root /var/www
   # chmod 0755 /var/www
   # chown -R root:root /var/www/cgi-bin
   # chmod 0755 /var/www/cgi-bin
   # chmod -R 0755 /var/www/cgi-bin/cgi_wrapper