Sudo before 1.9.17p1 allows local users to obtain root access because /etc/nsswitch.conf from a user-controlled directory is used with the --chroot option.
Sudo before 1.9.5p2 contains an off-by-one error that can result in a heap-based buffer overflow, which allows privilege escalation to root via "sudoedit -s" and a command-line argument that ends with a single backslash character.