There is a group-utmp-to-root privilege escalation vulnerability in
/bin/login in Debian, and I expect in all other Linux distros.
For details and exploit please see
 
http://bugs.debian.org/505271 
 
Currently am not aware of any group utmp issues (that could be
leveraged to get root).

Cheers,

Paul Szabo psz@maths.usyd.edu.au http://www.maths.usyd.edu.au/u/psz/ 
School of Mathematics and Statistics   University of Sydney    Australia