Issue 1:
Users are always granted permissions to cd into a directory. The
check for whether execute is present on directories is a de-facto
no-op. This cannot be mitigated without upgrading. Even setting
an explicit "deny - execute" NFSv4 ACE will be bypassed.
Issue 2:
All ACEs for the owner_group (group@) and regular groups
(group:<foo>) are granted the current user. This means that
POSIX mode 770 is de-facto 777, and the below ACL is also de-facto
777 because the groupmember check for builtin_administrators
returns True.
root@TESTBOX[~]# getfacl testfile
# file: testfile
# owner: root
# group: wheel
group:builtin_administrators:rwxpDdaARWcCos:-------:allow