CERT mailing list archives

AA20-020A: Critical Vulnerability in Citrix Application Delivery Controller, Gateway, and SD-WAN WANOP

From: "US-CERT" <US-CERT () ncas us-cert gov>
Date: Mon, 20 Jan 2020 16:20:20 -0600
CISA Logo

National Cyber Awareness System:

AA20-020A: Critical Vulnerability in Citrix Application Delivery Controller, Gateway, and SD-WAN WANOP [ 
https://www.us-cert.gov/ncas/alerts/aa20-020a ] 01/20/2020 1:15 PM EST 



Original release date: January 20, 2020 
Summary

On January 19, 2020, Citrix released firmware updates for Citrix Application Delivery Controller (ADC) and Citrix 
Gateway versions 11.1 and 12.0 to address CVE-2019-19781. Citrix expects to release updates for other vulnerable 
versions of Citrix ADC, Gateway, and SD-WAN WANOP appliances through January 24, 2020. (See Mitigations for update 
schedule).[1] [ https://support.citrix.com/article/CTX267027 ]

A remote, unauthenticated attacker could exploit CVE-2019-19781 to perform arbitrary code execution.[2] [ 
https://support.citrix.com/article/CTX267027 ] This vulnerability has been detected in exploits in the wild.[3] [ 
https://www.ncsc.gov.uk/news/citrix-alert ]

The Cybersecurity and Infrastructure Agency (CISA) strongly recommends that all users and administrators upgrade their 
vulnerable appliances as soon as possible once the appropriate firmware update becomes available.

Timeline of Specific Events

  * December 17, 2019  Citrix releases Security Bulletin CTX267027 with mitigations steps. 
  * January 8, 2020  The CERT Coordination Center (CERT/CC) releases Vulnerability Note VU#619785: Citrix Application 
Delivery Controller and Citrix Gateway Web Server Vulnerability, [4] [ https://www.kb.cert.org/vuls/id/619785/ ] and 
CISA releases a Current Activity entry.[5] [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/08/citrix-application-delivery-controller-and-citrix-gateway ] 
  * January 10, 2020  The National Security Agency (NSA) releases a Cybersecurity Advisory on CVE-2019-19781.[6] [ 
https://media.defense.gov/2020/Jan/10/2002233132/-1/-1/0/CSA%20FOR%20CITRIXADCANDCITRIXGATEWAY_20200109.PDF ] 
  * January 11, 2020  Citrix releases blog post on CVE-2019-19781 with timeline for fixes.[7] [ 
https://www.citrix.com/blogs/2020/01/11/citrix-provides-update-on-citrix-adc-citrix-gateway-vulnerability/ ] 
  * January 13, 2020  CISA releases a Current Activity entry describing their utility that enables users and 
administrators to test whether their Citrix ADC and Citrix Gateway firmware is susceptible to the CVE-2019-19781 
vulnerability.[8] [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/13/cisa-releases-test-citrix-adc-and-gateway-vulnerability ] 
  * January 16, 2020  Citrix announces that Citrix SD-WAN WANOP appliance is also vulnerable to CVE-2019-19781. 
  * January 19, 2020  Citrix releases firmware updates for Citrix ADC and Citrix Gateway versions 11.1 and 12.0 and 
blog post on accelerated schedule for fixes.[9] [ 
https://www.citrix.com/blogs/2020/01/19/vulnerability-update-first-permanent-fixes-available-timeline-accelerated/ ] 
  * January 24, 2020  Citrix expects to release firmware updates for Citrix ADC and Citrix Gateway versions 10.5, 12.1, 
and 13.0 and Citrix SD-WAN WANOP release 10.2.6 and 11.0.3. 

Technical Details

Impact

On December 17, 2019, Citrix reported vulnerability CVE-2019-19781. A remote, unauthenticated attacker could exploit 
this vulnerability to perform arbitrary code execution. This vulnerability has been detected in exploits in the wild.

The vulnerability affects the following appliances:


  * Citrix NetScaler ADC and NetScaler Gateway version 10.5  all supported builds 
  * Citrix ADC and NetScaler Gateway version 11.1  all supported builds before 11.1.63.15 
  * Citrix ADC and NetScaler Gateway version 12.0  all supported builds before 12.0.63.13 
  * Citrix ADC and NetScaler Gateway version 12.1  all supported builds 
  * Citrix ADC and Citrix Gateway version 13.0  all supported builds 
  * Citrix SD-WAN WANOP firmware and appliance models 4000, 4100, 5000, and 5100  all supported builds. (Citrix SD-WAN 
WANOP is vulnerable because it packages Citrix ADC as a load balancer). 

Detection Measures

CISA has released a utility that enables users and administrators to detect whether their Citrix ADC and Citrix Gateway 
firmware is susceptible to CVE-2019-19781.[10]  [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/13/cisa-releases-test-citrix-adc-and-gateway-vulnerability ]CISA 
encourages administrators to visit CISAs GitHub page [ https://github.com/cisagov/check-cve-2019-19781 ] to download 
and run the tool.

See the National Security Agencys Cybersecurity Advisory on CVE-2020-19781 for other detection measures.[11] [ 
https://media.defense.gov/2020/Jan/10/2002233132/-1/-1/0/CSA%20FOR%20CITRIXADCANDCITRIXGATEWAY_20200109.PDF ]

Mitigations

CISA strongly recommends users and administrators update Citrix ADC, Citrix Gateway, and Citrix SD-WAN WANOP once the 
appropriate firmware updates become available.

The fixed builds can be downloaded from Citrix Downloads pages for Citrix ADC [ 
https://www.citrix.com/downloads/citrix-adc/ ] and Citrix Gateway [ https://www.citrix.com/downloads/citrix-gateway/ ].

Until the appropriate update is accessible, users and administrators should apply Citrixs interim mitigation steps for 
CVE-2019-19781.[12] [ https://support.citrix.com/article/CTX267679 ] Verify the successful application of the above 
mitigations by using the tool in CTX269180  CVE-2019-19781  Verification ToolTest [ 
https://support.citrix.com/article/CTX269180 ].* Note:* these mitigation steps apply to Citrix ADC and SD-WAN WANOP 
deployments.[13] [ https://support.citrix.com/article/CTX267027 ]

Refer to table 1 for Citrixs planned fix schedule.[14] [ https://support.citrix.com/article/CTX267027 ]

*Table 1. Fix schedule for Citrix appliances vulnerable to CVE-2019-19781*

*Vulnerable Appliance* *Firmware Update* *Release Date* Citrix ADC and Citrix Gateway version 10.5 Refresh Build 
10.5.70.x January 24, 2020 (Expected) Citrix ADC and Citrix Gateway version 11.1 Refresh Build 11.1.63.15 January 19, 
2020 Citrix ADC and Citrix Gateway version 12.0 Refresh Build 12.0.63.13 January 19, 2020 Citrix ADC and Citrix Gateway 
version 12.1 Refresh Build 12.1.55.x January 24, 2020 (Expected) Citrix ADC and Citrix Gateway version 13.0 Refresh 
Build 13.0.47.x January 24, 2020 (Expected) Citrix SD-WAN WANOP Release 10.2.6 Citrix ADC Release 11.1.51.615 January 
24, 2020 (Expected) Citrix SD-WAN WANOP Release 11.0.3 Citrix ADC Release 11.1.51.615 January 24, 2020 (Expected) 



Administrators should review NSAs Citrix Advisory [ 
https://media.defense.gov/2020/Jan/10/2002233132/-1/-1/0/CSA%20FOR%20CITRIXADCANDCITRIXGATEWAY_20200109.PDF ] for other 
mitigations, such as applying the following defense-in-depth strategy:

Consider deploying a VPN capability using standardized protocols, preferably ones listed on the National Information 
Assurance Partnership (NIAP) Product Compliant List (PCL), in front of publicly accessible Citrix ADC and Citrix 
Gateway appliances to require user authentication for the VPN before being able to reach these appliances. Use of a 
proprietary SSLVPN/TLSVPN is discouraged.

References
[1] Citrix Security Bulletin CTX267027, Vulnerability in Citrix Application Del [ 
https://support.citrix.com/article/CTX267027 ] [2] Citrix Security Bulletin CTX267027, Vulnerability in Citrix 
Application Del [ https://support.citrix.com/article/CTX267027 ] [3] United Kingdom National Cyber Secrity Centre 
(NCSC) Alert: Actors exploitin [ https://www.ncsc.gov.uk/news/citrix-alert ] [4] CERT/CC Vulnerability Note VU#619785  
[ https://www.kb.cert.org/vuls/id/619785/ ] [5] CISA Current Activity: Citrix Application Delivery Controller and 
Citrix Ga [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/08/citrix-application-delivery-controller-and-citrix-gateway ] 
[6] NSA Cybersecurity Advisory: Mitigate CVE-2019-19781: Critical Vulnerability [ 
https://media.defense.gov/2020/Jan/10/2002233132/-1/-1/0/CSA%20FOR%20CITRIXADCANDCITRIXGATEWAY_20200109.PDF ] [7] 
Citrix blog: Citrix provides update on Citrix ADC, Citrix Gateway vulnerabi [ 
https://www.citrix.com/blogs/2020/01/11/citrix-provides-update-on-citrix-adc-citrix-gateway-vulnerability/ ] [8] CISA 
Current Activity: CISA Releases Test for Citrix ADC and Gateway Vulner [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/13/cisa-releases-test-citrix-adc-and-gateway-vulnerability ] [9] 
Citrix Blog: Vulnerability Update: First permanent fixes available, timelin [ 
https://www.citrix.com/blogs/2020/01/19/vulnerability-update-first-permanent-fixes-available-timeline-accelerated/ ] 
[10] CISA Current Activity: CISA Releases Test for Citrix ADC and Gateway Vulne [ 
https://www.us-cert.gov/ncas/current-activity/2020/01/13/cisa-releases-test-citrix-adc-and-gateway-vulnerability ] [11] 
NSA Cybersecurity Advisory: Mitigate CVE-2019-19781: Critical Vulnerabilit [ 
https://media.defense.gov/2020/Jan/10/2002233132/-1/-1/0/CSA%20FOR%20CITRIXADCANDCITRIXGATEWAY_20200109.PDF ] [12] 
Citrix Security Bulletin CTX267679, Mitigation Steps for CVE-2019-19781  [ https://support.citrix.com/article/CTX267679 
] [13] Citrix Security Bulletin CTX267027, Vulnerability in Citrix Application De [ 
https://support.citrix.com/article/CTX267027 ] [14] Citrix Security Bulletin CTX267027, Vulnerability in Citrix 
Application De [ https://support.citrix.com/article/CTX267027 ] 
Revisions
January 20, 2020: Initial Version ________________________________________________________________________

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AA20-020A: Critical Vulnerability in Citrix Application Delivery Controller, Gateway, and SD-WAN WANOP US-CERT (Jan 20)
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