I have just discovered a regular expression that crashes the router. I suspect the error is because of division by zero. Since I work for the Enterprise, I do not have direct access to TAC. Please somebody report this to Cisco. I have tested it on ranges of routers (2611, 2821, 2851, 7206) and IOSes (12.0-12.4). All routers crashed with some type of BUS ERROR.
Command can be issued in user mode, therefore I think it can be considered as vulnerability to potentially cause DOS.
I do not know a better way to report this, so I am posting it here.