Installing this security update hangs my Mac.

Here are some things to try:

Boot into recovery (CMD-R) and use Disk Utility to check and repair your disk's file system. Start at the lowest level of the drive and work your way up to the container level and disk level.

Then disconnect all external devices and boot into safe mode and try the update in safe mode. This may help if something that you have installed is interfering with the security update. For instance, extensions that "clean" your system, anti-virus utilities, other things that embed themselves and run in the background. Even in safe mode some of these extensions can be intrusive and interfere with updates.

If all else fails, you can make two backups (two is better than one), disconnect all devices, boot into recovery, erase/format your disk and install a fresh new operating system. You must have reliable backups before erasing your disk. On first boot, create one new user with administrator privileges, with a different name that any of your previous accounts. Don't install anything at this point. Apply all OS updates, including the security update, with that single account active. With a blank system like this, if you can't get past the security update, it is time to have your hardware checked. Assuming the update does work, then connect your backup and run migration assistant to migrate over your accounts, files (but no settings and no applications). Then reinstall your applications from scratch, re-establish settings, printers, etc. This minimizes (but does not guarantee) the chances that you will encounter this in the future.

I used the above process when I had this same problem in High Sierra with a security update. It did succeed. Others in this forum may have some better ideas.

Hello WDMTX,

We understand that you're running into an issue installing an update on your Mac, and we want to help.

You mentioned that the system hangs and you have to do a hard reset; can you let us know more about the steps you're taking to reset your Mac? Are you referring to restarting your Mac, or something else?

Are you using these steps to update your Mac? How to update the software on your Mac

If you are using the above steps, are you seeing any specific error messages when you attempt to install the update? If so, what does the error say?

If you're seeing an error stating more available space is needed, please check out this page for some great information on how to manage your Mac storage: How to free up storage space on your Mac

Thanks!