I assume your EntireX Broker is running on z/OS, so EXX v8.1.3 has long been out of support. We’re currently running v9.10 on z/OS 2.1, which has been out of support also.
You can get a chart of EXX versions and their various end-of-maintenance dates in Empower, but the oldest one listed is v9.0.1 which went EOM on 2016-06-30.
One complicating factor is the OS version. Software AG only certifies a product with an OS is the OS is supported. z/OS 1.13 is certified through EXX v9.9, which went EOM on 2018-10-31 (earlier if you count when the OS version went EOM). Now, this doesn’t mean newer versions of EXX won’t work on the older OSs, but if you encounter any issue due to incompatibility between the product and OS, you won’t get a fix for it. z/OS 2.1 buys you compatibility through v9.12, but it is possible newer versions up through v10.5 might still run on z/OS 2.1.
For CICS, you can reference https://www.softwareag.com/corporate/images/CICS-zOS-20191015_tcm389-187459.pdf, but it only indicates compatibility with CICS TS 5.2 through 5.5. We don’t use CICS with EntireX… just batch Natural RPC Servers, so I cannot advise on any issues you might run into outside of that.