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

medium Nessus Plugin ID 96959

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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.

Solution

Apply the appropriate patch according to the vendor advisory.

See Also

https://xenbits.xen.org/xsa/advisory-203.html

https://xenbits.xen.org/gitweb/?p=xen.git;a=summary

Plugin Details

Severity: Medium

ID: 96959

File Name: xen_server_XSA-203.nasl

Version: 1.7

Type: local

Family: Misc.

Published: 2/2/2017

Updated: 7/10/2020

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: Low

Base Score: 2.1

Temporal Score: 1.6

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

CVSS Score Source: CVE-2016-10025

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:xen:xen

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

Exploit Ease: No known exploits are available

Patch Publication Date: 12/21/2016

Vulnerability Publication Date: 12/21/2016

Reference Information

CVE: CVE-2016-10025

BID: 95026

IAVB: 2017-B-0008-S