"Connection to server lost" after upgrading Fedora 25 to 26

Nextcloud version: 12.0.0
Operating system and version: Fedora 26
Apache or nginx version: Apache/2.4.26
PHP version: 7.1.6
Is this the first time you’ve seen this error?: yes

Can you reliably replicate it? (If so, please outline steps):

  1. Enter website url.
  2. After this you cans see error “Connection to server lost” and this web page (only pure html):

The issue you are facing:
After upgrading to Fedora 26 (PHP upgraded too) all websites on my server works correctly, besides Nextcloud. I also can’t sync my calendar through DAVdroid. One time Apache process load 100% CPU.

The output of your Nextcloud log in Admin > Logging:

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

The output of your Apache/nginx/system log in /var/log/____:

This problem in apache http2 module https://bz.apache.org/bugzilla/show_bug.cgi?id=6123