Citrix XenServer Multiple Vulnerabilities (CTX219378)

low Nessus Plugin ID 96778
New! Plugin Severity Now Using CVSS v3

The calculated severity for Plugins has been updated to use CVSS v3 by default. Plugins that do not have a CVSS v3 score will fall back to CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.


A server virtualization platform installed on the remote host is affected by multiple vulnerabilities.


The version of Citrix XenServer installed on the remote host is missing a security hotfix. It is, therefore, affected by multiple vulnerabilities :

- A flaw exists in x86 instruction CMPXCHG8B due to legacy operand size overrides not being properly ignored when handling prefixes. A guest attacker can exploit this to disclose potentially sensitive information on the host system. Note that the ability to read a small amount of hypervisor memory is restricted to privileged-mode code in all guests except on Citrix XenServer 6.2 SP1 and 6.0.2CC, where the attack may also be performed from non-privileged-mode code in HVM guest VMs.

- A denial of service vulnerability exists when a guest asynchronously modifies its instruction stream to effect the clearing of EFLAGS.IF. A guest attacker can exploit this to cause the host to hang or crash.

- A denial of service vulnerability exists due to a NULL pointer dereference flaw that is triggered when the hvmemul_vmfunc() function pointer uses inappropriate NULL checks before indirect function calls. A guest attacker can exploit this to cause the hypervisor to crash. Note that the ability of privileged-mode code in HVM guest VMs to crash the host is restricted to AMD systems running Citrix XenServer 7.0. (CVE-2016-10025)


Apply the appropriate hotfix according to the vendor advisory.

See Also

Plugin Details

Severity: Low

ID: 96778

File Name: citrix_xenserver_CTX219378.nasl

Version: 1.8

Type: local

Family: Misc.

Published: 1/25/2017

Updated: 11/13/2019

Dependencies: citrix_xenserver_version.nbin

Risk Information

CVSS Score Source: CVE-2016-9932


Risk Factor: Medium

Score: 4.4


Risk Factor: Low

Base Score: 2.1

Temporal Score: 1.6

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

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


Risk Factor: Low

Base Score: 3.3

Temporal Score: 2.9

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

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

Vulnerability Information

CPE: cpe:/a:citrix:xenserver

Required KB Items: Host/XenServer/version, Host/local_checks_enabled

Exploit Ease: No known exploits are available

Patch Publication Date: 12/21/2016

Vulnerability Publication Date: 12/13/2016

Reference Information

CVE: CVE-2016-9932, CVE-2016-10024, CVE-2016-10025

BID: 94863, 95021, 95026