Crash report begins. Anonymous machine information:

BLADe182

amd64
11.2-RELEASE-p10
FreeBSD 11.2-RELEASE-p10 #9 4a2bfdce133(RELENG_2_4_4): Wed May 15 18:54:42 EDT 2019 root@buildbot1-nyi.netgate.com:/build/ce-crossbuild-244/obj/amd64/ZfGpH5cd/build/ce-crossbuild-244/pfSense/tmp/FreeBSD-src/sys/pfSense

Crash report details:

PHP Errors:
[27-Jan-2020 20:33:31 Europe/Kiev] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 5268998136 bytes) in /usr/local/www/suricata/suricata_logs_browser.php on line 54
[27-Jan-2020 20:33:36 Europe/Kiev] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 7629163976 bytes) in /usr/local/www/suricata/suricata_logs_browser.php on line 54

bmeeks

A quick forum search with this error information will uncover lots of posts that give you the cause and the fix.

Short version is the log file you are trying to open and view is too large to be read into the available PHP memory. Enable automatic log management on the LOGS MGMT tab and don't let your log files get so large. Or else don't try to view them via the LOGS VIEW tab and instead open them with a third-party editor from a command-line session. Or better still, export them off the firewall into a SIEM-type server.

This is a limitation of the PHP sub-system that the GUI works on top of.