pam_per_user before 0.4 does not verify if the user name changes between authentication attempts and uses the same subrequest handle, which…

pam_per_user before 0.4 does not verify if the user name changes between authentication attempts and uses the same subrequest handle, which allows remote attackers or local users to login as other users by using certain applications that allow the username to be changed during authentication, such as /bin/login.