Ubuntu Security Notice USN-778-1 – It was discovered that cron did not properly check the return code of the setgid() and initgroups() system calls. A local attacker could use this to escalate group privileges. Please note that cron versions 3.0pl1-64 and later were already patched to address the more serious setuid() check referred to by CVE-2006-2607.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/78030/USN-778-1.txt
Source: https://packetstormsecurity.com/files/78030/Ubuntu-Security-Notice-778-1.html