There is a possible tty hijacking in shadow 4.x before 4.1.5 and sudo 1.x before 1.7.4 via "su - user -c program". The user session can be escaped to the parent session by using the TIOCSTI ioctl to push characters into the input buffer to be read by the next process.
useradd in shadow-utils before 4.0.3, and possibly other versions before 4.0.8, does not provide a required argument to the open function when creating a new user mailbox, which causes the mailbox to be created with unpredictable permissions and possibly allows attackers to read or modify the mailbox.