Xen Intel VMX hvmemul_vmfunc() NULL Pointer Dereference DoS (XSA-203)

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 NULL pointer dereference flaw due to a
failure to utilize necessary NULL checks before doing indirect
function calls through the hvmemul_vmfunc() function pointer. A guest
attacker can exploit this issue to cause the hypervisor to crash,
resulting in a denial of service condition.

Please note the following items :

- Only HVM guests can exploit the vulnerability. PV guests
cannot exploit the vulnerability.

- Only x86 systems are vulnerable that use SVM (AMD
virtualization extensions) rather than VMX (Intel
virtualization extensions). This applies to HVM guests
on AMD x86 CPUs. Therefore, AMD x86 hardware is
vulnerable whereas Intel hardware is not.

- ARM systems are not affected by 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-203.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: 96959 ()

Bugtraq ID: 95026

CVE ID: CVE-2016-10025

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