Root compromise is possible in kernels 2.2.x (x <= 19) up through 2.4.y.
(y <= 9).
Here's more info:
http://www.securityfocus.com/cgi-bin/archive.pl?id=1&mid=221337&start=2001-10-15&end=2001-10-21
If you've got a system with multiple users, please upgrade your kernel.
~M