ESB-2021.2222 – [Virtual] Citrix Hypervisor 8.2 LTSR: Denial of service – Existing account

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AUSCERT External Security Bulletin Redistribution

ESB-2021.2222
Citrix Hypervisor Security Update
24 June 2021

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AusCERT Security Bulletin Summary
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Product: Citrix Hypervisor 8.2 LTSR
Publisher: Citrix
Operating System: Virtualisation
Impact/Access: Denial of Service — Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-20257 CVE-2021-3416

Reference: ESB-2021.1314
ESB-2021.1210

Original Bulletin:
https://support.citrix.com/article/CTX316325

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Citrix Hypervisor Security Update

Reference: CTX316325
Category : Medium
Created : 23 June 2021
Modified : 23 June 2021

Applicable Products

o Citrix Hypervisor

Description of Problem

Two security issues have been identified in Citrix Hypervisor 8.2 LTSR, each of
which may allow privileged code in a guest VM to cause the host to crash or
become unresponsive. These issues only affect Citrix Hypervisor 8.2 LTSR.
These issues have the following CVE identifiers:

o CVE-2021-3416
o CVE-2021-20257

+————–+————————————+————————-+
|CVE ID |Description |Pre-conditions |
+————–+————————————+————————-+
| |privileged code in a guest VM may |must be able to execute |
|CVE-2021-3416 |cause the host to crash or become |privileged code in the |
| |unresponsive |guest VM |
+————–+————————————+————————-+
| |privileged code in a guest VM may |must be able to execute |
|CVE-2021-20257|cause the host to crash or become |privileged code in the |
| |unresponsive |guest VM |
+————–+————————————+————————-+

What Customers Should Do

Citrix has released a hotfix to address these issues. Citrix recommends that
affected customers install this hotfix as their patching schedule allows. The
hotfix can be downloaded from the following locations:
Citrix Hypervisor 8.2 LTSR: CTX310674 – https://support.citrix.com/article/
CTX310674

What Citrix is Doing

Citrix is notifying customers and channel partners about this potential
security issue. This article is also available from the Citrix Knowledge Center
at https://support.citrix.com/ .

Obtaining Support on This Issue

If you require technical assistance with this issue, please contact Citrix
Technical Support. Contact details for Citrix Technical Support are available
at https://www.citrix.com/support/open-a-support-case/ .

Reporting Security Vulnerabilities to Citrix

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 see the following webpage: https://www.citrix.com/about/
trust-center/vulnerability-process.html .

Disclaimer

This document is provided on an “as is” basis and does not imply any kind of
guarantee or warranty, including the warranties of merchantability or fitness
for a particular use. Your use of the information on the document is at your
own risk. Citrix reserves the right to change or update this document at any
time.

Changelog

Date Change
2021-06-23 Initial Publication

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You have received this e-mail bulletin as a result of your organisation’s
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.

NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT’s members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation’s
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.

NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author’s website to ensure that the information is still current.

Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:

https://www.auscert.org.au/bulletins/

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
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