CVE-2017-13649
UnrealIRCd 4.0.13 and earlier creates a PID file after dropping privileges to a non-root account, which might allow local users to kill arbitrary processes by leveraging access to this non-root account for PID file modification before a root script executes a "kill `cat /pathname`" command. NOTE: the vendor indicates that there is no common or recommended scenario in which a root script would execute this kill command.
Source: CVE-2017-13649