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Xen IOMMU page mapping issues on x86 (XSA-378)

medium Nessus Plugin ID 159518

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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 affected by multiple vulnerabilities in IOMMU page mapping on x86.
 Both AMD and Intel allow ACPI tables to specify regions of memory which should be left untranslated, which typically means these addresses should pass the translation phase unaltered. While these are typically device specific ACPI properties, they can also be specified to apply to a range of devices, or even all devices. On all systems with such regions Xen failed to prevent guests from undoing/replacing such mappings.

 - On all systems with such regions Xen failed to prevent guests from undoing/replacing such mappings. (CVE-2021-28694)

 - On AMD systems, where a discontinuous range is specified by firmware, the supposedly-excluded middle range will also be identity-mapped. (CVE-2021-28695)

 - On AMD systems, upon de-assigment of a physical device from a guest, the identity mappings would be left in place, allowing a guest continued access to ranges of memory which it shouldn't have access to anymore. (CVE-2021-28696)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Apply the appropriate patch according to the vendor advisory.

See Also

https://xenbits.xen.org/xsa/advisory-378.html

Plugin Details

Severity: Medium

ID: 159518

File Name: xen_server_XSA-378.nasl

Version: 1.3

Type: local

Family: Misc.

Published: 4/5/2022

Updated: 4/27/2022

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.9

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

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

CVSS Score Source: CVE-2021-28696

CVSS v3

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5.9

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

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

Vulnerability Information

CPE: cpe:/o:xen:xen

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

Exploit Ease: No known exploits are available

Patch Publication Date: 8/25/2021

Vulnerability Publication Date: 8/25/2021

Reference Information

CVE: CVE-2021-28694, CVE-2021-28695, CVE-2021-28696

IAVB: 2021-B-0061-S