crontab.c in crontab in FreeBSD and Apple Mac OS X allows local users to (1) determine the existence of arbitrary files via a symlink attack on a /tmp/crontab.XXXXXXXXXX temporary file and (2) perform MD5 checksum comparisons on arbitrary pairs of files via two symlink attacks on /tmp/crontab.XXXXXXXXXX temporary files.
https://exchange.xforce.ibmcloud.com/vulnerabilities/65899
http://www.securityfocus.com/bid/46604
http://www.securityfocus.com/archive/1/516716/100/0/threaded