Hardlink before 0.1.2 suffer from multiple stack-based buffer overflow flaws because of the way directory trees with deeply nested directories are processed. A remote attacker could provide a specially-crafted directory tree, and trick the local user into consolidating it, leading to hardlink executable crash, or, potentially arbitrary code execution with the privileges of the user running the hardlink executable.
https://www.openwall.com/lists/oss-security/2011/10/20/6
https://security-tracker.debian.org/tracker/CVE-2011-3630
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2011-3630