Hardlink before 0.1.2 operates on full file system objects path names which can allow a local attacker to use this flaw to conduct symlink attacks.
https://www.openwall.com/lists/oss-security/2011/10/20/6
https://security-tracker.debian.org/tracker/CVE-2011-3632
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2011-3632