FreeBSD VuXML: Documenting security issues in FreeBSD and the FreeBSD Ports Collection

xen-kernel -- x86: Mishandling of instruction pointer truncation during emulation

Affected packages
xen-kernel = 4.5.3
xen-kernel = 4.6.3
4.7.0 <= xen-kernel < 4.7.1


VuXML ID 49211361-ba4d-11e6-ae1b-002590263bf5
Discovery 2016-09-08
Entry 2016-12-04

The Xen Project reports:

When emulating HVM instructions, Xen uses a small i-cache for fetches from guest memory. The code that handles cache misses does not check if the address from which it fetched lies within the cache before blindly writing to it. As such it is possible for the guest to overwrite hypervisor memory.

It is currently believed that the only way to trigger this bug is to use the way that Xen currently incorrectly wraps CS:IP in 16 bit modes. The included patch prevents such wrapping.

A malicious HVM guest administrator can escalate their privilege to that of the host.


CVE Name CVE-2016-7093
FreeBSD PR ports/214936