NOTE: This post comes from Esther Barthel, MSc, solutions architect, owner of cognition IT, and a consultant to ControlUp.

On December 17, 2019, Citrix released a security bulletin detailing a vulnerability in Citrix Application Delivery Controller (ADC), formerly known as NetScaler ADC, and Citrix Gateway, formerly known as NetScaler Gateway, that could lead to arbitrary code execution. In response, our Citrix ADC expert Esther Barthel created a script to help ControlUp customers detect whether or not their Citrix ADC appliance is vulnerable or if the suggested remediation has been applied.

The resulting script checks whether or not the mitigated action is configured and globally bound on NetScaler/Citrix ADC and supports the responder policy configuration. Note that this script will not perform the shell nsapimgr mitigation to avoid a potential loss of admin functionality. This script will state this as a warning as well when it is run.

The script works with a couple of arguments to trigger additional functionality/actions:

Script Action: NetScaler/Citrix ADC 1

When all parameters are configured for the default value No, the script will only perform a check:

Script Action: NetScaler/Citrix ADC 2

Setting configure mitigation parameter to Yes will configure the mitigation responder policy and ensure that the policy is globally bound:

Script Action: NetScaler/Citrix ADC 3

Script Action: NetScaler/Citrix ADC 4

If needed, you can trigger a rollback using the script by configuring the Perform Rollback argument to Yes:

Script Action: NetScaler/Citrix ADC 5

The responder policy information is based on the information retrieved with the performed check:

Script Action: NetScaler/Citrix ADC 6

Citrix suggests a reboot to ensure any connections using the vulnerability are killed, so the script includes an argument that can be configured to Yes when needed:

Script Action: NetScaler/Citrix ADC 7

Script Action: NetScaler/Citrix ADC 8

Note: Unfortunately this script is not interactive, so you can’t cancel a reboot by killing the script execution. Esther has included it in the script in case you want to run the PowerShell script as a standalone action.

To learn more about this script, go to the ControlUp Script Library and search for Check for Citrix ADC CVE-2019-19781 Vulnerability Mitigation. ControlUp customers can download the script from the ControlUp console.

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