Problem:
In Nagios XI versions 5.4.0 and 5.4.1 there was a bug in the included Nagios Core version which caused a segmentation fault (crash) in some systems.
Resolution:
First and foremost, please take an XI backup (and a VM snapshot if possible) so that you can revert if necessary:
https://assets.nagios.com/downloads/nagiosxi/docs/Backing-Up-And-Restoring-Nagios-XI.pdf
We have fixed the segfault issue, and you can run the following commands to fix this on a running 5.4.0 or 5.4.1 system:
Then transfer the attached file to your XI server and run these commands from the directory containing the patch:
service nagios stop
killall -9 nagios
service ndo2db stop
service mysqld restart
for i in `ipcs -q | grep nagios |awk '{print $2}'`; do ipcrm -q $i; done
tar zxf ndoutils_segfault_patched.tar.gz
cd ndoutils_segfault_patched
./upgrade