Xen x86 CR0.TS and CR0.EM Honoring Cross-task Register State Information Disclosure (XSA-190)

This script is Copyright (C) 2016-2017 Tenable Network Security, Inc.


Synopsis :

The remote Xen hypervisor installation is missing a security update.

Description :

According to its self-reported version number, the Xen hypervisor
installed on the remote host is affected by an information disclosure
vulnerability in x86_emulate.c due to a failure to properly honor
CR0.TS and CR0.EM. A local attacker within an x86 HVM guest operating
system can exploit this, by modifying an instruction while the
hypervisor is preparing to emulate it, to read or manipulate FPU, MMX,
or XMM register state information for other tasks running in the
guest.

Note that Nessus has checked the changeset versions based on the
xen.git change log. Nessus did not check guest hardware configurations
or if patches were applied manually to the source code before a
recompile and reinstall.

See also :

https://xenbits.xen.org/xsa/advisory-190.html
https://xenbits.xen.org/gitweb/?p=xen.git;a=summary

Solution :

Apply the appropriate patch according to the vendor advisory.

Risk factor :

Low / CVSS Base Score : 3.3
(CVSS2#AV:L/AC:M/Au:N/C:P/I:P/A:N)
CVSS Temporal Score : 2.4
(CVSS2#E:U/RL:OF/RC:C)
Public Exploit Available : false

Family: Misc.

Nessus Plugin ID: 94162 ()

Bugtraq ID: 93344

CVE ID: CVE-2016-7777

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