Yesterday really serious security bug was found in FreeBSD (from 7.1 to 8.0). Using public exploit local user can gain root privileges on vulnerable system. Below is an easy way solution to fix this terrible bug:
% cd /usr/src/libexec/rtld-elf/
% fetch http://people.freebsd.org/~cperciva/rtld.patch
% cat rtld.patch | patch -p1
% make && make install && make clean
Thanks to soko1 from truebsd.org.