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Security advisories | Jan 27, 2020

UPDATE - Citrix Releases Critical Security Patches

The Threat:

UPDATE: As of January 24th, 2020, Citrix has released security patches for all affected versions of Citrix ADC, SD-WAN WANOP, and Citrix Gateway products 1]. There has been confirmed exploitation of this vulnerability by at least one prominent ransomware threat actor group [2]. Due to the widespread exploitation of this vulnerability it is highly recommended that organizations apply security patches for all affected Citrix products as soon as possible. After security patches are applied, the previously recommended mitigation actions are no longer required; however, eSentire suggests running the Citrix/FireEye tool to verify that a previous compromise has not occurred.

On January 19th, 2020, Citrix released patches for two vulnerable versions of Citrix ADC and Citrix Gateway products [1]. These patches address the critical code execution vulnerability reported in previous advisories [3]. This vulnerability is being actively exploited in the wild for multiple malicious purposes; it is highly recommended to apply the available patches as soon as possible.

What we’re doing about it:

  • Known scanner and payload IP addresses associated with attacks exploiting this vulnerability have been added to the eSentire Global Blacklist
  • MVS (formerly esRECON) has plugins to identify the vulnerability CVE-2019-19781
    • esLOG+ rules have been deployed to detect this vulnerability
    • This applies only to clients that are providing HTTPREQUEST Netscaler Logs. Please reach out to [email protected] if you have questions regarding netscaler logging.
  • esLOG+ customers have been reviewed for signs of Citrix exploitation

What you should do about it:

  • Apply relevant Citrix issued security patches as soon as possible. [1]
  • Citrix, in conjunction with FireEye, released a security tool which can be used to validate whether Citrix systems have been previously compromised [4]

Additional information:

CVE-2019-19781 allows simple directory traversal by a remote attacker in Citrix Application Delivery Controller (ADC) and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. Additionally, the vulnerability affects the Citrix SD-WAN WANOP appliance, versions 10.2.6 and 11.0.3.

It should be noted that the mitigation actions supplied by Citrix do not work on Citrix ADC and Citrix Gateway Release "12.1 build 50.28". If running this build, users will need update to version 12.1 build 50.28/50.31 or later. 

Patch Release [1]

Citrix ADC Version

Patch Release Date

13

Jan 23, 2020 

12.1

Jan 23, 2020 

12

Jan 19, 2020 

11.1

Jan 19, 2020 

10.5

Jan 24, 2020 

Citrix SD-WAN WANOP 

Patch Release Date

10.2.6

Jan 22, 2020 

11.0.3

Jan 22, 2020 

References:

[1] https://support.citrix.com/article/CTX267027

[2] https://www.zdnet.com/article/hackers-target-unpatched-citrix-servers-to-deploy-ransomware/

[3] https://www.esentire.com/security-advisories/critical-update-to-citrix-vulnerability-exploited/

[4] https://www.fireeye.com/blog/products-and-services/2020/01/fireeye-and-citrix-tool-scans-for-iocs-related-to-vulnerability.html