lib/xymond_ipc.c in Xymon 4.1.x, 4.2.x, and 4.3.x before 4.3.25 use weak permissions (666) for an unspecified IPC message queue, which allows local users to inject arbitrary messages by writing to that queue.
https://sourceforge.net/p/xymon/code/7891/
http://www.securityfocus.com/archive/1/537522/100/0/threaded