Xen Asynchronous Modification EFLAGS.IF Clearing DoS (XSA-202)

This script is Copyright (C) 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 missing a security update. It is,
therefore, affected by a denial of service vulnerability due to a flaw
in the x86 instruction emulator whenever a guest asynchronously
modifies its instruction stream to effect the clearing of EFLAGS.IF.
An attacker who has guest kernel administrator privileges can exploit
this issue to cause the host to hang or crash.

Please note the following items :

- Only x86 PV guests can exploit the vulnerability.

- Neither ARM guests nor x86 HVM guests can exploit the
vulnerability.

Note that Nessus has not tested for this vulnerability but has instead
relied only on 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-202.html
https://xenbits.xen.org/gitweb/?p=xen.git;a=summary

Solution :

Apply the appropriate patch according to the vendor advisory.

Risk factor :

Medium / CVSS Base Score : 5.5
(CVSS2#AV:A/AC:L/Au:S/C:N/I:N/A:C)
CVSS Temporal Score : 4.5
(CVSS2#E:F/RL:OF/RC:ND)
Public Exploit Available : true

Family: Misc.

Nessus Plugin ID: 96958 ()

Bugtraq ID: 95021

CVE ID: CVE-2016-10024

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