https://arstechnica.com/information-technology/2020/01/as-attacks-begin-citrix-ships-patch-for-vpn-vulnerability/

On January 19, Citrix released some permanent fixes to a vulnerability on the company's Citrix Application Delivery Controller (ADC) and Citrix Gateway virtual private network servers that allowed an attacker to remotely execute code on the gateway without needing a login. The vulnerability affects tens of thousands of known VPN servers, including at least 260 VPN servers associated with US federal, state, and local government agencies—including at least one site operated by the US Army.

The patches are for versions 11.1 and 12.0 of the products, formerly marketed under the NetScaler name. Other patches will be available on January 24. These patches follow instructions for temporary fixes the company provided to deflect the crafted requests associated with the vulnerability, which could be used by an attacker to gain access to the networks protected by the VPNs.