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AUSCERT External Security Bulletin Redistribution
ESB-2021.1089
Citrix Hypervisor Security Update
31 March 2021
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AusCERT Security Bulletin Summary
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Product: Citrix Hypervisor
Publisher: Citrix
Operating System: Virtualisation
Citrix XenServer
Impact/Access: Denial of Service -- Existing Account
Reduced Security -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-28688 CVE-2021-28038 CVE-2020-35498
Reference: ESB-2021.1086
ESB-2021.0837
Original Bulletin:
https://support.citrix.com/article/CTX306565
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Citrix Hypervisor Security Update
Reference: CTX306565
Category : Medium
Created : 30 March 2021
Modified : 30 March 2021
Applicable Products
o Citrix Hypervisor
Description of Problem
Two security issues have been identified in Citrix Hypervisor (formerly Citrix
XenServer) that may allow privileged code in a guest VM to cause the host to
crash or become unresponsive.
These issues affect all currently supported versions of Citrix Hypervisor up to
and including Citrix Hypervisor 8.2 LTSR.
These issues have the following identifiers:
CVE ID Description Type Pre-requisites
An attacker with the ability to CWE-400: Ability to run
CVE-2021-28038 execute privileged mode code in a Uncontrolled privileged
guest can perform a denial of Resource code in a
service attack against the host Consumption guest VM
An attacker with the ability to CWE-400: Ability to run
CVE-2021-28688 execute privileged mode code in a Uncontrolled privileged
guest can perform a denial of Resource code in a
service attack against the host Consumption guest VM
An additional issue has been identified in Citrix Hypervisor 8.2 LTSR (only)
that may allow malicious network traffic to cause subsequent packets to be
dropped.
This issue has the following identifier:
CVE ID Description Type Pre-requisites
Malicious network traffic on the CWE-682: Access to the
CVE-2020-35498 local network may cause subsequent Incorrect local network
packets to be dropped Calculation
What Customers Should Do
Citrix has released hotfixes to address these issues. Citrix recommends that
affected customers install these hotfixes as their patching schedule allows.
The hotfixes can be downloaded from the following locations:
Citrix Hypervisor 8.2 LTSR: CTX306481 - https://support.citrix.com/article/
CTX306481 and CTX306423 - https://support.citrix.com/article/CTX306423
Citrix XenServer 7.1 LTSR CU2: CTX306480 - https://support.citrix.com/article/
CTX306480
Citrix XenServer 7.0: CTX306482 - https://support.citrix.com/article/CTX306482
Citrix is notifying customers and channel partners about this potential
security issue. This article is also available from the Citrix Knowledge Center
at . If you require technical assistance with this issue, please contact Citrix
Technical Support. Contact details for Citrix Technical Support are available
at .
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
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
2021-03-30 Initial Publication
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