Nagios XI versions prior to 2011R1.9 contain privilege escalation vulnerabilities in the scripts that install or update system crontab entries. Due to time-of-check/time-of-use race conditions and missing synchronization or final-path validation, a local low-privileged user could manipulate filesystem state during crontab installation to influence the files or commands executed with elevated privileges, resulting in execution with higher privileges.
The product checks the state of a resource before using that resource, but the resource’s state can change between the check and the use in a way that invalidates the results of the check.