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

Low Nessus Plugin ID 94162


The remote Xen hypervisor installation is missing a security update.


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.


Apply the appropriate patch according to the vendor advisory.

See Also



Plugin Details

Severity: Low

ID: 94162

File Name: xen_server_XSA-190.nasl

Version: $Revision: 1.5 $

Type: local

Family: Misc.

Published: 2016/10/20

Modified: 2017/02/03

Dependencies: 78089

Risk Information

Risk Factor: Low


Base Score: 3.3

Temporal Score: 2.4

Vector: CVSS2#AV:L/AC:M/Au:N/C:P/I:P/A:N

Temporal Vector: CVSS2#E:U/RL:OF/RC:C


Base Score: 6.3

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Vulnerability Information

CPE: cpe:/o:xen:xen

Required KB Items: installed_sw/Xen Hypervisor, Settings/ParanoidReport

Exploit Available: false

Exploit Ease: No known exploits are available

Patch Publication Date: 2016/10/04

Vulnerability Publication Date: 2016/10/04

Reference Information

CVE: CVE-2016-7777

BID: 93344

OSVDB: 145066

IAVB: 2016-B-0149