Directory traversal vulnerability in device-linux.c in the router advertisement daemon (radvd) before 1.8.2 allows local users to overwrite arbitrary files, and remote attackers to overwrite certain files, via a .. (dot dot) in an interface name. NOTE: this can be leveraged with a symlink to overwrite arbitrary files.
https://github.com/reubenhwk/radvd/commit/92e22ca23e52066da2258df8c76a2dca8a428bcc
http://www.ubuntu.com/usn/USN-1257-1
http://www.openwall.com/lists/oss-security/2011/10/06/3