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For production deployment issues, please contact the TAC! We will not comment or assist with your TAC case in these forums.
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ISE 2.2 uses RHEL (Red Hat Enterprise Linux) 7 as found here:
Keep in mind that ISE is sold as an appliance, so general vulnerabilities for a particular RHEL distribution do not always apply to the appliance if those services are not running or exposed externally. ISE patches will incorporate updates for known vulnerabilities to underlying OS. If suspect a particular vulnerability, then be sure to contact TAC for additional follow up.