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