This is a message posted by Syzop on unrealircd forum:

Here's a heads up (preannouncement), so UnrealIRCd admins know they should pay attention next Friday:

Internally we discovered a serious issue in UnrealIRCd. A regular user can cause UnrealIRCd to crash, which results in all users being disconnected from the server. There is no other risk (no risk of remote code execution) but such a crash is serious enough to warrant this preannouncement and a fix soon.
This issue affects both UnrealIRCd 5 and UnrealIRCd 6. Fixed versions will be released on Friday, January 28 2022, at 16:00 GMT.
At the same date/time we will also release a "hot patch" so *NIX users can fix the issue without restart.

We recommend admins to apply the patch (or to upgrade) soon after it has been released on Friday. This is also why there is a preannouncement with an exact date and time, so people can be "ready".