Error creating rule: Unknown variable: MATCHED_VARS

Causes:

If you are getting this error, it means that you are using an old version of modsecurity that does not support the modern rule language and you are not running ASL or using aum to manage modsecurity. We recommend you install ASL or aum to manage modsecurity.

ASL and aum will not allow incompatible versions of the modsecurity rules to be installed.  They will also automatically upgrade mod_security provided you have UPDATE_TYPE set to "all", which is the default. If you have updates disabled in ASL or aum, then you will need to manually upgrade modsecurity:

yum upgrade mod_security

If you are not using ASL or aum, then you will need to upgrade modsecurity using whatever method you used to install it.