The default configuration of su in /etc/pam.d/su in GNU coreutils 5.2.1 allows local users to gain the privileges of a (1) locked or (2) expired account by entering the account name on the command line, related to improper use of the pam_succeed_if.so module.
Exploitability
AV:LAC:MAu:NImpact
C:PI:PA:P4.4/AV:L/AC:M/Au:N/C:P/I:P/A:P