CVE-2016-10024 Citrix CVE debrief

Who should care

Operators running Xen 4.8.x or affected Citrix XenServer releases, especially in environments that allow privileged paravirtualized guest administration.

Technical summary

NVD describes an availability issue in Xen through 4.8.0. On x86 PV guests, a guest kernel administrator can alter the instruction stream asynchronously while certain kernel operations are in progress, leading to host hang or crash. The NVD record maps the weakness to CWE-20 and lists affected Citrix XenServer releases 6.0.2, 6.2.0, 6.5, and 7.0.

Defensive priority

Medium — prioritize patching on any affected Xen or XenServer host because the impact is host-level availability loss, but exploitation requires local high-privilege guest access.

Recommended defensive actions

• Apply the vendor fix referenced by Xen Security Advisory XSA-202 and the Citrix CTX219378 advisory across affected hosts.
• Upgrade or replace Xen 4.8.x and the affected Citrix XenServer releases identified in the NVD CPE criteria.
• Restrict who can administer guest kernels on x86 PV guests; treat guest kernel administrators as highly trusted.
• Verify patch status across all hypervisor nodes and plan maintenance windows to safely restart or recycle hosts if needed.

Evidence notes

The supplied NVD record states that Xen through 4.8.0 is affected and that local x86 PV guest OS kernel administrators can cause a host hang or crash by modifying the instruction stream asynchronously during certain kernel operations. The same record lists affected Citrix XenServer versions and includes references to Xen advisory XSA-202, Citrix CTX219378, Debian DSA-3847, and Gentoo GLSA-201612-56. NVD also classifies the weakness as CWE-20.

Official resources