fusermount in FUSE before 2.7.5, and 2.8.x before 2.8.2, allows local users to unmount an arbitrary FUSE filesystem share via a symlink attack on a mountpoint.
fuse 2.8.5 and earlier does not properly handle when /etc/mtab cannot be updated, which allows local users to unmount arbitrary directories via a symlink attack.
Certain legacy functionality in fusermount in fuse 2.8.5 and earlier, when util-linux does not support the --no-canonicalize option, allows local users to bypass intended access restrictions and unmount arbitrary directories via a symlink attack.