If you get 500 Internal Service Error with WordPress, and you are using ModSecurity, here is how to solve the problem:

1, You try to visit your front page, and see this error:
Error Message:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, innovita@gmail.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

2, Check http log file

tail /var/log/httpd/patentdb-error.log

You see

 ModSecurity: Output filter: Response body too large (over limit of 524288, total not specified)

3, Now you can fix it:
Open file with vi /etc/httpd/modsecurity.d/modsecurity_crs_10_config.conf, you will see these lines:

SecRequestBodyAccess On
SecResponseBodyAccess On
SecResponseBodyMimeType (null) text/html text/plain text/xml
SecResponseBodyLimit 524288

Change 524288 to larger value, or change option ‘SecResponseBodyAccess’ to Off, save and restart apache

apachectl restart