Multiple vulnerabilities have been discovered in Citrix ADC (formerly known as NetScaler ADC), Citrix Gateway (formerly known as NetScaler Gateway) and Citrix SD-WAN WANOP appliance models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabilities, if exploited, could result in a number of security issues including:

Attacks that are limited to the management interface

• System compromise by an unauthenticated user on the management network.
• System compromise through Cross Site Scripting (XSS) on the management interface
• Creation of a download link for the device which, if downloaded and then executed by an unauthenticated user on the management network, may result in the compromise of their local computer.

Mitigating Factors: Customers who have configured their systems in accordance with Citrix recommendations in https://docs.citrix.com/en-us/citrix-adc/citrix-adc-secure-deployment/secure-deployment-guide.html have significantly reduced their risk from attacks to the management interface.

Attacks that are applicable to a Virtual IP (VIP)

• Denial of service against either the Gateway or Authentication virtual servers by an unauthenticated user (the load balancing virtual server is unaffected).
• Remote port scanning of the internal network by an authenticated Citrix Gateway user. Attackers can only discern whether a TLS connection is possible with the port and cannot communicate further with the end devices. 

Mitigating Factors: Customers who have not enabled either the Gateway or Authentication virtual servers are not at risk from attacks that are applicable to those servers. Other virtual servers e.g. load balancing and content switching virtual servers are not affected by these issues.

In addition, a vulnerability has been found in Citrix Gateway Plug-in for Linux that would allow a local logged-on user of a Linux system with that plug-in installed to elevate their privileges to an administrator account on that computer.
 

The issues have the following identifiers:  

The following versions of Citrix ADC, Citrix Gateway and Citrix SD-WAN WANOP remediate the vulnerabilities: 

• Citrix ADC and Citrix Gateway 13.0-58.30 and later releases
• Citrix ADC and NetScaler Gateway 12.1-57.18 and later 12.1 releases
• Citrix ADC and NetScaler Gateway 12.0-63.21 and later 12.0 releases
• Citrix ADC and NetScaler Gateway 11.1-64.14 and later 11.1 releases
• NetScaler ADC and NetScaler Gateway 10.5-70.18 and later 10.5 releases
• Citrix ADC FIPS 12.1-55.179 and later releases
• Citrix SD-WAN WANOP 11.1.1a and later releases
• Citrix SD-WAN WANOP 11.0.3d and later 11.0 releases
• Citrix SD-WAN WANOP 10.2.7 and later 10.2 releases
• Citrix Gateway Plug-in for Linux 1.0.0.137 and later versions

Fixed builds have been released for all supported versions of Citrix ADC, Citrix Gateway and Citrix SD-WAN WANOP. Citrix strongly recommends that customers immediately install these updates. 

The latest builds can be downloaded from https://www.citrix.com/downloads/citrix-adc/ and https://www.citrix.com/downloads/citrix-gateway/ and https://www.citrix.com/downloads/citrix-sd-wan/.

Customers who are unable to immediately update to the latest version are advised ensure access to the management interface is restricted. Please see https://docs.citrix.com/en-us/citrix-adc/citrix-adc-secure-deployment/secure-deployment-guide.html for more information. 

Users with Citrix Gateway Plug-in for Linux should log-in to an updated version of Citrix Gateway and select ‘Network VPN mode’. Citrix Gateway will then prompt the user to update. 

Customers with Citrix-managed Citrix Gateway service do not need to take any action.

Citrix thanks Laurent Geyer of Akamai, Muris Kurgas of Digital 14 (Xen1thLabs), Maarten Boone (@staatsgeheim), Donny Maasland (@donnymaasland), Albert Shi of Univision Network (Shanghai) Co., Ltd and Viktor Dragomiretskyy for working with us to protect Citrix customers.

Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. For details on our vulnerability response process and guidance on how to report security-related issues to Citrix, please visit the Citrix Trust Center at https://www.citrix.com/about/trust-center/vulnerability-process.html.