Citrix XenServer Multiple Security Updates

A number of security vulnerabilities have been identified in Citrix XenServer that may allow a malicious administrator of a guest VM to compromise the host.

These vulnerabilities affect all currently supported versions of Citrix XenServer up to and including Citrix XenServer 7.2.

The following vulnerabilities have been addressed:

• CVE-2017-12134: (High) linux: Fix Xen block IO merge-ability calculation
• CVE-2017-12135: (Medium) multiple problems with transitive grants
• CVE-2017-12136: (High) grant_table: Race conditions with maptrack free list handling
• CVE-2017-12137: (High) x86: PV privilege escalation via map_grant_ref
• CVE-2017-12855: (Low) grant_table: possibly premature clearing of GTF_writing / GTF_reading

For Citrix XenServer installations using both version 6.2 SP1 or earlier and also HVM guests only, the risk of a host compromise is replaced by a risk of a host crash.

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 7.2: CTX226375– https://support.citrix.com/article/CTX226375 and CTX226378 – https://support.citrix.com/article/CTX226378

Citrix XenServer 7.1: CTX226298 – https://support.citrix.com/article/CTX226298 and CTX226299 – https://support.citrix.com/article/CTX226299

Citrix XenServer 7.0: CTX226374 – https://support.citrix.com/article/CTX226374 and CTX226377 – https://support.citrix.com/article/CTX226377

Citrix XenServer 6.5 SP1: CTX226373 – https://support.citrix.com/article/CTX226373 and CTX226376 – https://support.citrix.com/article/CTX226376

Citrix XenServer 6.2 SP1: CTX226372 – https://support.citrix.com/article/CTX226372

Citrix XenServer 6.0.2 Common Criteria: CTX226371 – https://support.citrix.com/article/CTX226371

Customers who are using the Live Patching feature of Citrix XenServer 7.2 may apply the relevant hotfix without requiring a reboot.