Citrix Released Permanent Fixes for the Actively Exploited CVE-2019-19781 Flaw in ADC 11.1 and 12.0

Citrix released permanent fixes for CVE-2019-19781 Flaw in ADC 11.1 and 12.0, which would allow an unauthenticated remote attacker to execute arbitrary code on the vulnerable system.

The vulnerability was discovered by Dmitry Serebryannikov from Positive Technologies and the severity of the vulnerability is high. The following are the affected versions.

• Citrix ADC and Citrix Gateway version 13.0 all supported builds
• Citrix ADC and NetScaler Gateway version 12.1 all supported builds
• Citrix ADC and NetScaler Gateway version 12.0 all supported builds
• Citrix ADC and NetScaler Gateway version 11.1 all supported builds
• Citrix NetScaler ADC and NetScaler Gateway version 10.5 all supported builds

Permanent Fixes Released

Citrix releases permanent fixes for ADC versions 11.1 and 12.0 and it can be downloaded from here and here.

The fixes applicable for “Citrix ADC and Citrix Gateway Virtual Appliances (VPX) hosted on any of ESX, Hyper-V, KVM, XenServer, Azure, AWS, GCP or on a Citrix ADC Service Delivery Appliance (SDX). SVM on SDX does not need to be updated.”

“It is necessary to upgrade all Citrix ADC and Citrix Gateway 11.1 instances (MPX or VPX) to build 11.1.63.15 to install the security vulnerability fixes. It is necessary to upgrade all Citrix ADC and Citrix Gateway 12.0 instances (MPX or VPX) to build 12.0.63.13 to install the security vulnerability fixes.”

Citrix ADC and Citrix Gateway
Version	Refresh Build	Release Date
10.5	10.5.70.x	24th January 2020
11.1	11.1.63.15	19th January 2020 (Released)
12.0	12.0.63.13	19th January 2020 (Released)
12.1	12.1.55.x	24th January 2020
13.0	13.0.47.x	24th January 2020
Citrix SD-WAN WANOP
Release	Citrix ADC Release	Release Date
10.2.6	11.1.51.615	24th January 2020
11.0.3	11.1.51.615	24th January 2020

Urgent Patch Required

Since the PoC released attackers started exploiting the flaw to install backdoors on the vulnerable machines. Citrix urges users to apply the fix immediately.

Once the patches applied, you can use the verification tool to ensure the patches have been applied correctly.

Also, CISA released a test tool for administrators and users to check for Citrix Application Delivery Controller (ADC) and Citrix Gateway vulnerability. The tool can be downloaded from GitHub.

Related Coverage

1. CISA Releases Test Tool for Citrix ADC and Gateway Vulnerability – Sysadmins Can Test Now
2. PoC Exploit Code Released for Citrix ACD and Gateway Remote Code Execution Vulnerability
3. Hackers Scanning for Citrix Servers Vulnerable to Remote Code Execution
4. Critical Vulnerability in Citrix Products Let Hackers Access to 80,000 Companies Internal Network