Vulmon
Description of Problem
A number of security vulnerabilities have been identified in Citrix XenServer that may allow malicious privileged code running within a guest VM to compromise the host.
These vulnerabilities affect all currently supported versions of Citrix XenServer up to and including Citrix XenServer 7.0.
The following vulnerabilities have been addressed:
- CVE-2016-7092 (High): x86: Disallow L3 recursive pagetable for 32-bit guests
- CVE-2016-7093 (High): x86: Mishandling of instruction pointer truncation during emulation
- CVE-2016-7094 (Medium): x86 HVM: Overflow of sh_ctxt->seg_reg[]
- CVE-2016-7154 (High): use after free in FIFO event channel code
Mitigating Factors
Customers using Citrix XenServer 7.0 where all guests are 64-bit PV guests are unaffected.
Customers using Citrix XenServer 6.2SP1 and earlier with no 32-bit PV guests are unaffected unless there are HVM guests using shadow paging in which case the impact is reduced to a possible host crash rather than a host compromise.
What Customers Should Do
Hotfixes have been released to address these issues. Citrix strongly recommends that affected customers install these hotfixes, which can be downloaded from the following locations:
Citrix XenServer 7.0: CTX216463 – https://support.citrix.com/article/CTX216463
Citrix XenServer 6.5 SP1: CTX216462 – https://support.citrix.com/article/CTX216462
Citrix XenServer 6.2 SP1: CTX216461 – https://support.citrix.com/article/CTX216461
Citrix XenServer 6.1: CTX216460 – https://support.citrix.com/article/CTX216460
Citrix XenServer 6.0.2: CTX216458 – https://support.citrix.com/article/CTX216458
Citrix XenServer 6.0.2 Common Criteria: CTX216459 – https://support.citrix.com/article/CTX216459
Citrix XenServer 6.0: CTX216457 – https://support.citrix.com/article/CTX216457
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 http://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.html.
Reporting Security Vulnerabilities
Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. For guidance on how to report security-related issues to Citrix, please see the following document: CTX081743 – Reporting Security Issues to Citrix