The NFS client implementation in the kernel in Red Hat Enterprise Linux (RHEL) 3, when a filesystem is mounted with the noacl option, checks permissions for the open system call via vfs_permission (mode bits) data rather than an NFS ACCESS call to the server, which allows local client processes to obtain a false success status from open calls that the server would deny, and possibly obtain sensitive information about file permissions on the server, as demonstrated in a root_squash environment.  NOTE: it is uncertain whether any scenarios involving this issue cross privilege boundaries.