Updated PAM packages are now available. These packages correct a bug in pam_xauth's handling of authorization data for the root user. [Updated 12 March 2003] Added packages for CentOS Linux ES and CentOS Linux WS
The pam_xauth module is used to forward xauth information from user to user in applications such as the su command. Andreas Beck discovered that pam_xauth will forward authorization information from the root account to unprivileged users. This could be used by a local attacker to gain access to an administrator's X session. To exploit this vulnerability the attacker would have to get the administrator, as root, to use su to access the account belonging to the attacker. Users of pam_xauth are advised to upgrade to these errata packages which contain a patch which adds ACL (access control list) functionality to pam_xauth and disallows root forwarding by default. Thanks to Andreas Beck for reporting this issue.