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.
The problem can be corrected by updating your system to the following package versions:
1 June 2009
A security issue affects these releases of Ubuntu and its derivatives:
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.
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
In general, a standard system upgrade is sufficient to effect the necessary changes.