Vulmon
Description of Problem
A number of security vulnerabilities have been identified in Citrix XenServer that may allow malicious 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.
For releases before Citrix XenServer 7.0, these issues may allow malicious user-mode code in HVM guests and malicious privileged-mode code in PV guests to compromise the host.
For Citrix XenServer 7.0, these issues may allow malicious privileged-mode code in guests to compromise the host.
In addition, on Intel-based XenServer 7.0 systems, malicious user-mode code in HVM guests may be able to crash the guest VM. On AMD-based XenServer 7.0 systems, malicious user-mode code in HVM guests may be able to compromise the guest VM. However, these processor specific attacks are operating-system dependent and Citrix is not aware of any operating systems that permit such attacks.
The following vulnerabilities have been addressed:
- CVE-2016-9379, CVE-2016-9380: delimiter injection vulnerabilities in pygrub
- CVE-2016-9381: qemu incautious about shared ring processing
- CVE-2016-9382: x86 task switch to VM86 mode mis-handled
- CVE-2016-9383: x86 64-bit bit test instruction emulation broken
- CVE-2016-9385: x86 segment base write emulation lacking canonical address checks
- CVE-2016-9386: x86 null segments not always treated as unusable
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: CTX218899 – https://support.citrix.com/article/CTX218899 and CTX218900 – https://support.citrix.com/article/CTX218900 and CTX218902 – https://support.citrix.com/article/CTX218902
Citrix XenServer 6.5 SP1: CTX218898 – https://support.citrix.com/article/CTX218898 and CTX218901 – https://support.citrix.com/article/CTX218901
Citrix XenServer 6.2 SP1: CTX218897 – https://support.citrix.com/article/CTX218897
Citrix XenServer 6.0.2 Common Criteria: CTX218896 – https://support.citrix.com/article/CTX218896
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
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